Combat (and other activity) Underwater

[Ts_]

Originally Posted by davidtmoore

Those are drowning rules.

Okay, they make a lot of sense in that respect. But they also cover long distance swimming, and swimming at different speeds.

Originally Posted by davidtmoore

If you're swimming normally, you shouldn't be having a problem.

Well, there is a +3 modifier if you're in the water voluntarily. And I guess swimming in a pool isn't exactly "adventure grade" skill usage at +0, either.

Originally Posted by davidtmoore

If you're diving, use the breath-holding rules instead.

But that means that diving is independent of the Swimming skill, and actually does not require any other skill roll either. I find that strange, even though I admit that diving and swimming are quite different motions.

Anyway, thanks for the info! I'll just let people drown more often instead of letting them dive. ;)
Ts

[topper]

Cool thread and nice rule set you have made. (I have taken Davidtmoore´s as that seemed balanced and was finished.)
Now let´s see if it works in reality too ;)

Edit: When going through your rules I disagree with four things:

*Dodge underwater is actually described in the rules. P.B.354: "Move equal to basic move/5 (round down)." But can be improved [/I]Move in other environments[/I] (P.B. 18): "You can improve water move directly for 5 pts per yard/second". This means that the avg. character underwater will have a dodge of 4 or 7 with the "step" back manouvre (that sucks yeh).
A good swimmer however would have 6/9 and one wearing flippers or webbed feet would probably get another +2 or so to move.
And with the bonuses to dodge from underwater attack, dodges seem pretty okay underwater actually.

*Why would aquatic creatures [I]not[I] be affected by the water when attacking?

*½ blowback should only be against weapons - actually the water confers momentum way better than air.

*The Bad sight (Far sighted) disadvantage. Why? If anything you´d be nearsighted. Though I personally would say that would only imply at murky water.

*Actually takedowns and pins underwater makes sense to me. Only difference is that usually a takedown takes the opponent down, here you get into a position where a pin is possible. Since none of the combatants can swim during a takedown or pin action the combatants will slowly descend into the deep... Until someone gets a pin on the opponent, then he is in such a position he can use his feet to paddle with for 2/3 normal swim speed.

[Bruno]

Originally Posted by topper

*Dodge underwater is actually described in the rules. P.B.354: "Move equal to basic move/5 (round down)." But can be improved Move in other environments (P.B. 18): "You can improve water move directly for 5 pts per yard/second". This means that the avg. character underwater will have a dodge of 4 or 7 with the "step" back manouvre (that sucks yeh).

Dodge isn't based on Move, or Basic Move - it's based on Basic Speed. It's important not to confuse the two, despite the annoyingly similar names, because of issues exactly like this one.

[Trachmyr]

I've tun some heavy underwater games before and have but together a "Gurps Aquatics" ruleset... see what you think.

(Part 1a: Advantages)

GURPS Aquatics



Basic Move		5/Level
	These rules supersede those given in the basic set. Basic Move costs +/- 5 points per level to increase or decrease. When increasing a either Ground or Water Move directly, apply a -20% accessibility limitation if increasing the mode above your Basic Move, or a -80% limitation if the increase would not exceed you Basic Move. Thus it costs only 1 point to raise either Ground or Water Move up to your Basic Move, but 4 points per level you increase it above your Basic Move. When reducing either Ground or Water Move directly, always apply a -80% accessibility limitation, making the cost only -1 point per level. You may not reduce either Ground or Water Move by more than two levels directly. Creatures with either 0 Ground or Water Movement (e.g., Aquatic) may not purchase Basic Move for a single mode, they can only raise or lower their full Basic Move at the normal +/-5 points per level.

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Amphibious		10
	This advantage represents any fully functional land creature that also has aquatic capabilities. For aquatic creatures with reduced land capabilities see the Aquatic Disadvantage. Amphibious creatures may gain Sprint bonuses in the water, they may retreat in the water, and they may learn the Long Distance Swimming skill. See the Basic Set for other details. Below are given new limitations that can be applied to this advantage; they are mutually exclusive.
	Modifier: Semi-Amphibious. Your Water Move is based on ½ of your Basic Move, although you still get sprint bonuses and can retreat. You suffer normal underwater penalties like a non-amphibious creature. However, you may substitute a basic HT roll for any swimming roll, you do not need to make a swimming roll when entering deep water, you make rolls versus panic when drowning at unmodified Will, and you still automatically stop drowning if you reach the surface. You may not substitute a basic DX roll in a contest of Aquabatics. You may use and learn the Long-Distance Swimming skill. 
	This limitation is normally -50%. However, if your Basic Move is only 2, this limitation is only worth -40%. If your Basic Move is less than 2, or if you want your Water Move to be equal to your full Basic Move, then the value of this limitation becomes only -30%.
	Modifier: Natural Swimmer. Like Semi-Amphibious, but your Water Move remains only 1/5 your Basic Move. You may not gain sprint bonuses or retreat, and you may not use or learn the Long-Distance Swimming skill. If instead you are an “Experienced Swimmer”, you must have purchased the Swimming Skill to at least HT level, but it makes this advantage suitable for Lifeguards, Scuba Instructors, Navy Seals and other people who have had a lot of experience in the water. 
	This limitation starts at -70% or -80% for “Experienced Swimmer”. Reduce the value of this limitation by 10% for each point that your Basic Move is less than 4, down to a minimum of -40% or -50% for “Experience Swimmer”.
	Modifier: Water Adapted. Your adaptation to the water has limited your mobility on land to some degree. You receive all the benefits of Amphibious while in the water, however your Ground Move is only ½ your Basic Move. You may still gain sprint bonuses and retreat, and use the Hiking and Running skills.
	This limitation is worth -30% if your Basic Move is 5 or higher, or -20% if less than 5. However, if your Basic Move is only 2, this limitation is only worth -10%. You may not take this limitation if your Basic Move is less than 2.

Ballast				1
	You must have Positive Buoyancy to take this perk. This allows you to choose every turn whether you have Positive or Negative Buoyancy, although carrying more than Heavy Encumbrance will still give you Negative Buoyancy, just as falling unconscious due to drowning will give you Negative Buoyancy. If you are unconscious or paralyzed otherwise, choose whether you remain at your current depth , rise at 1 yard/second or sink at 1 yard/second. This effect remains in place until you can once again take action.

Doesn’t Breathe			20
	Doesn’t Breathe (Gills) assumes that you can breathe all types of water, Freshwater, Brackish and Saltwater. However many creatures can only breathe one or two types. If you are purchasing this Advantage to be able to breathe water in addition to breathing air, use the following modifiers: All Water Types -50%, Saltwater and Brackish Water -60%, Saltwater -65%, Freshwater and Brackish Water -70%, Freshwater or Brackish Water -75%. If you cannot breathe air, then Gills changes from being a 0-point Feature to a Disadvantage worth: -2 for Saltwater & Brackish Water, -3 for Saltwater, -4 for Freshwater and Brackish Water or -5 for Freshwater or Brackish Water. You will suffocate as normal in the wrong type of water.
	Doesn’t Breathe (Oxygen Storage) allows you to store oxygen in both your body and your lungs. If you fail to take a deep breath, it does not reduce the time you can hold your breath. Taking a deep breath before you submerge will not increase the time you can hold your breath, but it will make you susceptible to the Bends. Hyperventilating has no effect on how long you can hold your breath, nor does breathing in pure oxygen, although it does affect the rate you replenish your internal oxygen supply.
	Every minute of normal breathing allows you to replenish 6 minutes of internal air, this increases to 10 minutes if breathing in pure oxygen. A successful Breath Control roll will allow you to replenish 10 minutes of air per minute of normal breathing, increased to 15 minutes if using pure oxygen. Breath Control does not allow you to increase the time you can cold our breath with a successful roll, but knowing Breath Control at HT level allows you to add +1 to your HT when calculating your internal air supply, knowing Breath Control at HT+1 level allows you to add +2 to your HT when calculating your internal air supply.

Finned				Var.
	You rely on fins or some form of propulsion other than legs to propel you through the water. You usually take the Feature No Legs (Aquatic) in order to take any of these options. If you rely on legs for only ground movement and Fins for water movement, then you may take this without the No Legs feature.
	These fins (you get two for free) can be targeted, can be armored and can strike a blow for Thr-1 damage at DX to hit, reach C, but a failed attack gives no risk of falling. If they cannot strike, this is a Quirk: Finned (No Attacks). You can also choose to buy Finned (Long Fins) as a 1-point Perk that can strike at reach 1. You may make attacks with Fins using only Brawling, but receive damage bonuses. 
	You may purchase extra Fins beyond two, take the Extra Legs advantage but specify the number of Fins. If you have both extra Fins and Legs, buy the Extra Leg advantage only once adding the total number of legs and fins together. Losing enough fins that would cause you to “fall” (one fin if you only have two), instead reduces Water Move to 1/3 normal. Loss of all fins reduces Water Move to 0, you may only float or sink based on your Buoyancy.
	You may choose to count a Striker as a Fin, this doesn’t change it’s base damage, and you do not need to count it when buying Extra Legs, although you gain the benefit as if it was an extra fin. Each Striker that can operate as a Fin requires a separate Perk: Striker as Fin. A fish’s tail is a good example of this.
	This can also represent Sails, Paddles or any other form of propulsion. Replace “Fin” with the appropriate form of propulsion. Note that many of these cannot strike blows, thus Paddles (No Attack) is a -1 point Quirk. If the body part is very fragile or must remain immobile and exposed, then not only can it not attack, but it also cannot be armored. This is a -5 point Disadvantage for being vulnerable, for instance, in the case of Sails (Vulnerable).
	
Nictating Membrane		1/Level
	Normal underwater penalty is -2 to vision when spotting something beyond one yard. This gives a penalty to combat rolls made at a reach greater than 1. On ranged attacks, calculate distance as if the target was twice as far as normal (or four times as far if combined with Nearsighted Bad Vision). Aquatic creatures suffer no vision penalties when underwater, but suffer these same penalties when above water.
	Nictating Membrane level 1 cuts these penalties in half. This is a -1 on vision and combat rolls beyond one yard, and calculate distance as if the target was 1.5x as far (three times if Nearsighted). Nictating Membrane Level 2+ removes these penalties entirely. Aquatic creatures may buy Nictating Membrane to improve their vision above the water.
	Modifier: Vision Only. Like normal you may see underwater (or above water if Aquatic) at no penalty, and your eyes are protected from mild irritants (those that don’t do actual HP damage). But you receive no bonus to HT rolls and gain no DR on your eyes. This is a -50% limitation that must be applied to exactly two levels of Nictating membrane for a final cost of 1 point.

[Trachmyr]

GURPS AQUATICS, Part 1b (Advantages)

Night Vision			1/Level
	As you descend into the depths of a body of water, it get dark very quickly. Night Vision helps reduce the penalties in low-light conditions. To determine the darkness penalty, take the square root of the depth in yards, dropping all fractions. Apply this penalty in addition to any low-light conditions that affect the surface of the water. If this number becomes -10 or worse, reduce it to -10 but it is completely dark, and Night Vision has no effect. At depths of 100 yards and below, total darkness applies. For example, if it is a gloomy day (-3 penalty) and you have dived to a depth of 25 yards (square root of 25 = 5), you will have a penalty of -8 due to darkness… while at 50 yards it is completely dark. This assumes clear water, the GM may apply further penalties for murky water, to a total maximum of -10 at which point Night Vision fails to work. Night Vision does not negate the penalties for murky water.
	Many deep dwelling aquatic creatures are either Blind or have the Perk: Bioluminescence, which allows you to generate light. Choose the brightness, but remember that a bright light also makes you much easier to spot, and creatures that aren’t blind are often attracted to light!

Pressure Support		1/Level
	You may purchase Pressure Support in 1 point levels, each level gives you improved resistance to high pressure environments. While pressure support changes the depth that the Bends and Nitrogen Narcosis becomes a danger, it does not give you any specific immunity to the bends, for that take either Resistant (Bends) or Doesn’t Breathe. You may take up to 10 levels of this advantage, if you have Pressure Support Level 10 and are Immune to the Bends, you become immune to the effects of all high pressures.
	Each level of pressure support roughly doubles the pressure when particular dangers develop. Level 1 gives 2x, level 2 is 4x, level 3 is 8x, level 4 is 16x, level 5 is 30x, level 6 is 60x, level 7 is 120x, level 8 is 250x, level 9 is 500x, level 10 is 1000x or full immunity if also immune to the bends.
	The Bends doesn’t become a risk until 2 pressures, but you can safely operate for 90 minutes. Reduce the safe operating time by 30 minutes for each additional pressure. At 3 pressures you can operate for 60 minutes and avoid the bends. At 4 pressures you can operate for 30 minutes before risking the bends. At 5 pressures, there is no safe diving time. At 10 pressures you must make a HT+3 roll (at -1 per 10 pressures) or take damage equal to the margin of failure (if SM is 2 or higher, multiply damage by SM).
	Nitrogen Narcosis is only a risk for those breathing pressurized air at depths, not for those who are holding their breath or using the Oxygen Storage Advantage. Using Helium instead of Nitrogen will completely avoid the risk, using a partial mixture of Helium will give HT bonuses up to +5. At 2.5 pressures, roll HT every 15 minutes or become Tipsy. At 5 pressures you automatically become Tipsy, and must make HT rolls every 15 minutes to avoid becoming Drunk.
	To find the depth for a particular pressure, multiply (Pressure-1) by 11 yards. A quick and dirty method is simply Pressure x 10 yards, although this is much more generous at lower depths and a bit less generous at deep depths.

Refraction Adjustment		1
	Through experience, you have become instinctively familiar with adjusting your attack to take refraction into account. You never suffer any penalties for attack through the surface of the water.

Resistant			Var.
	Resistance to the Bends also applies to Nitrogen Narcosis (Rapture of the Deep), but not to Oxygen Poisoning. The cost is 5 points for Immunity, 2 points for a +8 to HT, or 1 point for a +3 HT. For +30 minutes safe diving time, increase the cost by 1 point. For an additional 2 points, you get +60 minutes of safe diving time, or +90 minutes if you have the +8 HT bonus. You still reduce safe diving time by 30 minutes per pressure increase, so this means you can also dive further. Add 0.5 pressures to the point where Nitrogen Narcosis can make you ‘tipsy’ per extra 30 minutes of safe operating time, double the ‘Tipsy’ Depth to find the depth where Nitrogen Narcosis can make you ‘Drunk’. 

Temperature Tolerance 		1/Level
	At 100 yards of depth, water temperature begins to drop rapidly until it reaches about 40 degrees at the lower depths. Most of the change occurs between in the first 100 yards, dropping to around 55 degrees in most waters. This layer is called the thermocline. At about 300 yards the temperature reaches 50 degrees, at 500 yards it drops to 45 degrees, and below 1000 yards the temperature is about 40 degrees. In artic regions even the surface water can be as low as 28 degrees, the salinity keeps it from freezing, thus thermal shock becomes a danger. Most deep diving creatures will need one or two levels of Temperature Tolerance.
	At the bottom 20 degrees of your temperature range, below 55 degrees for normal humans, immersion hypothermia becomes a danger. Roll against HT every minute, failure indicates the loss of 1 FP. If in the bottom 10 degrees of your temperature range, below 45 degrees for a normal human, you lose 2 FP on a failure. Below your temperature range, 35 degrees for a normal human, you lose 1 FP even on a success, unless a critical success. Critical failures always doubles the FP lost. Do not apply modifiers for clothing or being wet, although a watertight insulated suit gives a +5 to HT, or +10 if Designed for Freezing conditions. If it’s a Heated suit, also reduce the FP lost due to immersion hypothermia by one.
	If you have lost even one FP point due to immersion hypothermia (or thermal shock) you begin shaking, giving a -2 DX. This shaking continues until you are no longer in danger of further FP loss due to cold, you have regained at least 1 FP, and your FP is once again positive. Shaking can also occur in normal cold conditions, but your FP must be reduced to less than one-half maximum before the condition occurs. 

Terrain Adaptation		5
	Terrain Adaptation (Water) negates Bad Footing and Water penalties when fighting in the water but not under it, and only if the water is less than waist deep. Likewise, Amphibious and Aquatic creatures only suffer bad footing penalties in water less than waist deep.
	If you have Negative Buoyancy, and that you have Terrain Adaptation (Water), you may also negate the Bad Footing effects while at the bottom of a body of water. You still suffer basic underwater penalties of -2 DX on all movement based skills and combat rolls, and a -1 on Active Defenses. However, your move is 1/5 Basic Move rather than being reduce to 1, and you may sprint while underwater. You may retreat underwater as long as you moved no more than your modified Move on your turn. You also gain sprint bonuses. You may calculate long distance travel based on the actual terrain being traversed.
	This assumes that the terrain at the bottom of the water is Stable, or that you have Terrain Adaptation for that terrain, if not, all Bad Footing effects and a maximum move of 1 still applies.

Underwater Weapon Mastery	1
	You may choose one weapon that you know how to use and that you have completely bought off the underwater attack penalty (if any) through the Underwater Combat Technique. You do damage with that weapon as if it were one level of Drag lower. If it already had Low Drag attacks, apply only a -1 damage penalty to the weapon, or no damage penalty if used while not completely underwater. You must specialize by weapon. Amphibious and Aquatic creatures (that are immune to normal underwater penalties) making Close Combat attacks are always treated as if not completely underwater.

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Accessibility Limitations		Var.
	The “Only in Water” limitation is worth only -20% for Aquatic and Amphibious characters, although “Not in the Water” is also worth -20% if the effect normally works underwater. For non-Aquatic and non-Amphibious characters, this is normally -30% for “Only in the Water” and -10% for “Not in the Water” if the effect normally works underwater.

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[Trachmyr]

GURPS AQUATICS, Part 2a (Disadvantages)

Aquatic				-10
	This disadvantage represents any fully functional water creature that also has limited or no land capabilities. It is incompatible with the Amphibious Advantage. An aquatic creature has a Ground Move of 0, and suffers a -6 DX to movement based skills and combat, and a -4 to Active Defenses, and cannot Dodge. You gain no sprint bonuses and cannot retreat. They are effectively “beached” on land, and require outside aid. Aquatic creatures are not eligible to purchase either Basic Move (Ground) or Terrain Adaptation. Aquatic creatures may not use or learn the Hiking or Running skills. Many aquatic creatures also have the No Legs (Aquatic) feature. 
	Aquatic creatures have no vision penalties while underwater, but have poorer vision out of the water, or when their head is above water. Calculate distance penalties to Vision as if the target was twice as far away, this applies a -2 penalty to Vision to spot something more than 1 yard away. This penalty applies to combat rolls made at greater than a Reach of 1. Also apply this penalty on all skill rolls for delicate tasks. Ignore this penalty if you have Nictating Membrane 2+, or reduce penalty to 1.5x range or -1 for Nictating Membrane level 1. If you are wearing a special water filled mask, you may also ignore this penalty.
	Aquatic creatures function without normal underwater penalties, and use their full Basic Move as their Water Move, but are not eligible to raise Water Move directly, they must purchase Basic Move at the normal cost of +/-5 points per level. This restriction on purchasing single modes of movement is lifted if you have either the Land Adapted or Semi-Aquatic limitations.
	All of the following limitations are mutually exclusive.
	Modifier: Limited Mobility. You may move very slowly outside of combat (or using 5 ready actions) at the rate of 1 yard per 5 seconds, much like a octopus can drag it’s body across a beach, or a fish flopping about. Roll HT for every yard traveled to avoid 1 FP loss from fatigue. This is a -50% limitation. If you rely on manipulators you become completely immobile if ½ or more are crippled. If you move by squirming or flopping, you become completely immobile when reduced to 0 HP or less.
	Modifier: Land Adapted. You have some degree of mobility on land. Your ground move is 1/5 your Basic Move, although you must treat all Terrain as Bad Footing. You may not gain sprint bonuses or retreat, and you may not use or learn the Hiking skill. You may learn the Running skill to improve your endurance on land, and you may learn Terrain Adaptation to buy off Bad Terrain penalties. This is a -100% limitation which converts the Aquatic Disadvantage into a 0-point feature.
	Modifier: Semi-Aquatic. While you have improved mobility on land, you are not fully adapted to aquatic environments. Your ground move is 1/2 your Basic Move, although you must treat all Terrain as Bad Footing. You may gain sprint bonuses and retreat on land, and you may use Hiking and Running skills. Many Semi-Aquatic creatures purchase the Terrain Adaptation advantage to buy-off Bad Terrain penalties for Stable, Ice, Water or Sand terrain. Note that sprinting is still impossible in Bad Footing. If Semi-Aquatic, you may choose if your vision is penalized underwater or above water.
	Your Water Move is equal to your full Basic Move, and you gain sprint bonuses and may retreat in the water. However, you suffer normal underwater penalties like a non-aquatic creature. You may still substitute a basic HT roll for any swimming roll, you do not need to make a swimming roll when entering deep water, you make rolls versus panic when drowning at unmodified Will, and you still automatically stop drowning if you reach the surface. You may not substitute a basic DX roll in a contest of  Aquabatics. You may use and learn the Long-Distance Swimming skill.
	This is a -100% limitation which converts the Aquatic Disadvantage into a 0-point feature. If instead, your Ground Move is only 1/5 Basic Move this is a -70% limitation if your Basic Move is 5 or higher (-80% if Basic Move is 4, or -90% if Basic Move is below 4); but it also prevents you from gaining sprint bonuses, retreating, and using the Hiking skill.

Cannot Float			-1
	In game terms this gives someone who would normally have Positive Buoyancy, Negative Buoyancy instead. It is incompatible with all versions of the Landbound Disadvantage. You will automatically sink 1 yard at the end of every turn, unless you sacrifice one movement to cancel this out.

Dependency			Var.
	Many aquatic creatures will have dependency on water in addition to having Gills, representing the fact that they dry out and wither. This is a Very Common substance on our world, but might change in other campaigns. Apply frequency modifiers as usual with “Hourly” and “Daily” being the most common choices.

Landbound			-10
	Your physiology makes you incapable of swimming or operating in the water. You have a Water Move of 0, and Negative Buoyancy, and always sink 1 yard at the end of your turn. You always receive a -6 DX to movement based skills and combat, and a -4 to Active Defenses, and cannot Dodge. You gain no sprint bonuses and cannot retreat. You cannot learn the Swimming or Long Distance Swimming Skills. Unless you do not need to breathe, you still can drown and make rolls to avoid drowning at HT-4!
	Modifier: Cannot Dive. If you can swim at the surface normally, but are unable to Dive underwater, then use this version instead. You have Positive Buoyancy, and you must always apply Buoyancy movement at the end of your turn. You use the penalties for Landbound only while underwater, otherwise use normal underwater penalties (and you may be Aquatic or Amphibious). You may learn the Swimming and Long Distance Swimming skills, but you may not use them while submerged. Unless you do not need to breathe, you still can drown. This limitation is worth -30% if you can carry Medium Encumbrance before gaining Negative Buoyancy, -50% for Heavy Encumbrance, or -70% if you can carry up to Extra-Heavy Encumbrance before gaining Negative Buoyancy.
	Modifier: Cannot Dive - Can Sink. This works exactly as the Cannot Dive variation, but you are at risk of gaining Negative Buoyancy whenever you take significant damage. If this happens you will sink below the surface and suffer full penalties. Choose if your Buoyancy comes from your Body or from your Head. If you take a Major Wound to that Body Part, you must roll HT (at -5 if it’s your head!) or gain Negative Buoyancy. Treat this as a Crippling Injury for healing purposes, except it cannot be Permanent. This limitation is 20% less than the equivalent Cannot Dive limitation, thus a -50% becomes a -30%.
	Modifier: Poor Diver. You can swim and operate as normal underwater, and your speed is unchanged, ignore all increased penalties for Landbound. However you have Positive Buoyancy and must always add buoyancy movement at the end of your turn. You can negate this automatic rise towards the surface by sacrificing 1 movement, but unless your Water Move is 2 or higher, you will not be able to dive. If you fall unconscious when you drown, you retain Positive Buoyancy, although you may still carry Heavy Encumbrance to gain Negative Buoyancy. This limitation is worth -90%, making it a -1 point Quirk.
	Modifier: Sinker. If you can walk along the bottom of a body of water and operate normally, but are unable swim while your feet are off the ‘ground’, then use this version instead. You have Negative Buoyancy, and you always sink 1 yard at the end of your turn. You use the penalties for Landbound only when not at the bottom of the water, otherwise use the standard penalties for Bad Footing Underwater. You may not learn the Swimming or Long Distance Swimming skills, but you may take Terrain Adaptation (Water) to improve mobility while walking along the bottom. Unless you do not need to breathe, you still can drown. This limitation is worth -50%.
	Modifier: Floater. Optionally, you may have Positive Buoyancy. You suffer all of the normal penalties associated with Landbound, including a Water Move of 0. However, you substitute a basic HT Roll for any swimming roll. You do not need to make a swimming roll when entering deep water, you make rolls versus panic when drowning at unmodified Will, and you always stop drowning if you reach the surface. This limitation is worth -30% if you can carry Medium Encumbrance before gaining Negative Buoyancy, -50% for Heavy Encumbrance, or -70% if you can carry up to Extra-Heavy Encumbrance before gaining Negative Buoyancy.  This limitation may also be taken in conjunction with Cannot Dive and Cannot Dive - Fragile. This limitation is 20% more than the equivalent Cannot Dive limitation, thus a -50% becomes a -70%. If taken in conjunction with Poor Diver, it becomes a 1-point Perk rather than a Quirk.
	Creatures with the Aquatic Disadvantage or the Amphibious Advantage cannot take Landbound, unless they take the Cannot Dive, Cannot Dive - Can Sink or Poor Diver versions of this Disadvantage. Likewise those that take Landbound without the Cannot Dive, Cannot Dive - Can Sink or Poor Diver variations may not purchase Ground or Water Move directly, nly normal Move at +/- 5 points per level.

[Trachmyr]

GURPS AQUATICS, Part 2b (Disadvantages)

No Legs				Var.
	No Legs (Aquatic) only means that you have no legs (they cannot be targeted and do not need armor) and that you cannot kick. Ignore all other modifiers and rules given, instead see the Aquatic Disadvantage. This is always a 0-point feature, do not apply any modifiers.
	No Legs (Semi-Aquatic) does not exist, use instead the No Legs (Aquatic) and the Aquatic Disadvantage with the Semi-Aquatic (or Land Adapted) limitations. You may also choose the Finned options listed above. If you have legs (or flippers!) that you walk on or swim with, then do not take No Legs (Aquatic). If they cannot kick, then take the Cannot Kick Disadvantage (-5 points, see extra legs for details).
	No Legs (Slithers) is a valid option for many Amphibious and Aquatic creatures that still have a ground move of at least 1. It affects ground movement only, thus can be combined with the Finned Features. Bought alone, the creature still requires legs for water movement, but if the creature Slithers (or rolls, bounces, etc.) in addition to having no legs for water movement, write this as No Legs (Aquatic - Slithers). Like both No Legs (Aquatic) and No Legs (Slithers) this is a 0-point Feature.

[Trachmyr]

GURPS AQUATICS, Part 3 (Skills)

Acrobatics			DX/Hard, Default: DX-6		Prerequisite: Ground Move 1+.
						      
	This skill cannot be used by those who lack a Ground Move score. Use Acrobatics rather than Aquabatics if at the bottom of a body of water and if you have Negative Buoyancy.

Aquabatics			DX/Hard, Default: DX-6		Prerequisite: Swimming or the ability to substitute HT for a swimming roll.
	This skill also allows you to outmaneuver an opponent or avoid being outmaneuvered when fighting at different levels while underwater. Additionally it can be rolled in place of a DX roll to avoid the additional penalties associated with a “knockdown” while underwater. Aquabatics is used rather than Acrobatics when at the bottom of a body of water if you have positive buoyancy.

Hiking				HT/Hard, Default: HT-5		Prerequisite: The ability to gain sprint	bonuses while running.
	A successful roll allows you to add +25% to distance when using overland travel. Knowing this skill at HT level gives a +1 HT bonus when rolling to avoid fatigue loss for long-distance travel. Knowing this skill at HT+1 level gives a +2 HT bonus to HT rolls versus fatigue from overland travel.

Long Distance Swimming	HT/Hard, Default: HT-5		Prerequisite: The ability to gain sprint bonuses while swimming.
	This skill works like Hiking but for long distance travel in water, giving you +25% to the distance traveled. Knowing this skill at HT level, gain +1 to HT rolls to avoid fatigue for long-distance swimming. If you know this skill at HT+1 level, add +2 to HT rolls to avoid fatigue loss for long-distance swimming.

Running			HT/Average, Default: HT-5		Prerequisite: Ground Move of 1 or higher.	
						
	In addition to it’s listed uses, you may substitute a Running roll for an HT roll to avoid increased fatigue loss for long-distance overland travel. Even though you are not actually running, the increased endurance you have trained for still applies.

Swimming			HT/Easy, Default: HT-4		Prerequisite: Water Move of 1 or higher.	
						
	Many Amphibious and Aquatic creatures do not take this skill at all, as they may make a basic HT roll in place of a Swimming roll, as well as drowning being much less of a risk. However, they may still take this skill, representing increased endurance, and functioning much like Running for land creatures.

Lifesaving			Hard Technique, Default: Prerequisite -5		Prerequisite: Swimming or the ability to substitute HT for a swimming roll.
	Maximum Level: Cannot exceed Prerequisite Skill (or HT if used as the prerequisite).
	Roll versus Lifesaving when attempting to rescue a drowning victim. Add or subtract the difference between your ST and the victim’s ST to the roll. Success stops the individual from drowning and gives you a grapple on your opponent (one or two hands, your choice). The victim must still make a swimming roll to avoid drowning if you let go. Failure indicates that you inhale some water, losing 1 FP. On a critical failure, the victim nearly drowned you, causing a loss of 6 FP. An opponent can roll an Active Defense to avoid being grappled, and this skill cannot be used on a resisting opponent that is neither stunned, immobilized or drowning.

Underwater Combat		Hard Technique, Default: Combat Skill - Var.      	
		Prerequisite: Swimming or the ability to substitute HT for a swimming roll, or the Landbound (Sinker) Disadvantage. Melee Combat or Weapon Skill.
	Maximum Level: May not reduce the penalty to less than half (unless Aquatic/Amphibious).
	You may buy off up to half of the drag penalty with the selected weapon. If the penalty varies by the mode of attack, use the worse penalty when determining this Techniques default. If fighting while not completely underwater, you gain a bonus to this technique equal to one-half of the normal penalty. Aquatic and Amphibious creatures (that are immune to normal underwater penalties) have only one-half normal drag penalties, and may completely buy off the drag penalty with this Technique, but they do not gain any bonus when not fighting completely underwater.

[Trachmyr]

GURPS AQUATICS, Part 4a (Rules)

Bad Footing
	You receive a -2 DX on all Movement based skills and DX rolls including all combat rolls. You also suffer -1 on all Active Defenses. Posture penalties apply only if they give a worse penalty, but are not cumulative with the Bad Footing penalties. All hexes cost one additional movement point to enter. You may not gain sprint bonuses. You may retreat (if allowed), but must make a DX roll (at the -2 DX penalty) or you fall, although you still gain the benefits of retreating, effectively diving for cover. 
	When calculating Hiking distance, remember that Bad Footing counts as Bad or Very Bad Terrain, and an Aquatic creature that lacks Terrain Adaptation (Stable) treats even good roads as Bad Terrain. This also applies to creatures that have traded in Terrain Adaptation (Stable) for another type of terrain as a racial feature. Sprinting speed with Bad Footing is ½ Ground Move (due to the increased movement costs, but a minimum of 1 yard/second), while normal paced running speed is ¼ Ground Move.

Ground Move of 0
	You receive a -6 DX on all Movement based skills and DX rolls including all combat rolls. You also suffer -4 on all Active Defenses, and cannot Dodge. This is effectively a Prone Posture, do not apply other Posture Penalties. Creatures with a move of 0 cannot gain sprint bonuses or retreat. They may still attack, parry or block at the given penalty.

Overland Travel
	These rules supersede those given in the basic set. Travel is measured in one half-hour intervals, requiring an HT roll to avoid increased fatigue loss. Under ideal conditions, travel distance is Move x 0.4 Miles, or Move x 0.5 miles with a successful Hiking roll. Apply modifiers for Terrain, Weather and Road Conditions to the distance traveled as normal.	
	Make an HT roll every 30 minutes, success indicates you lose one fatigue per encumbrance level. Failure indicate twice as much fatigue is lost! Bonuses from Fitness apply to these rolls, having Hiking at HT level also gives a +1 bonus to this HT roll, Hiking at HT+1 level gives a +2 HT bonus to the roll. You may substitute a roll versus Running skill for this HT, including all bonuses. Those with the Very Fit Advantage lose half this amount (round up), or roll versus HT for fatigue loss at twice the normal interval.  
	On a hot or cold day, you will also need to roll every 30 minutes to avoid the effects associated with inclement weather, see Cold or Heat for details. Regardless, those effects are in addition to the fatigue lost from travel, and can lead to serious injury in severe weather.

Bad Footing Underwater
	If you have a swim speed, you can swim along the bottom of a body of water as per normal swimming rules, the rules given here are used for those who choose to walk along the bottom of a body of water. They must be able to breathe or hold their breath (otherwise follow the rules for drowning), and they suffer all other effects for pressure and temperature. Calculate distance penalties to Vision as if the target was twice as far away, this applies a -2 penalty to Vision to spot something more than 1 yard away. This penalty applies to combat rolls made at greater than a Reach of 1. Ignore this penalty if you have Nictating Membrane 2+ (½ penalty for Nictating Membrane level 1), Aquatic, or if have you head above the water.
	If you do not have a swim speed or prefer not to use your swim speed and are at the bottom of a body of water, you may treat it as Bad Footing except that your movement becomes 1. Always calculate long-distance travel as if the terrain was Very Bad. Note that in this case this is not the same as a Water  Move, instead this is Ground Move used while underwater. 
	Combat underwater is very tiring. Any turn that you take any combat maneuver that includes an attack, you must make an unmodified HT roll or lose 1 FP.  Additionally, if you are holding your breath and you are hit with an attack Stuns you, make an additional HT or Breath Control roll at whatever penalty applied to the Stun roll, if you fail this HT roll you begin drowning. You may substitute Swimming rolls for these HT rolls if you choose. Knockback is also less effective, divide final knock back by 3 if in water, although a roll versus DX is still required to avoid “knockdown” if knock back would have been 1 or more yard before the divisor.
	You may take Terrain Adaptation (Water) to improve your underwater mobility, provided you have negative buoyancy. This assumes the terrain at the bottom is Stable, or that you have Terrain Adaptation for that terrain, if not, all Bad Footing effects and a maximum move of 1 still applies.

Underwater Penalties
	You receive a -2 DX on all Movement based skills and DX rolls including all combat rolls. You also suffer -1 on all Active Defenses. Posture penalties do not apply. You may only retreat if you are normally allowed to gain sprint bonuses underwater.
	Calculate distance penalties to Vision as if the target was twice as far away, this applies a -2 penalty to Vision to spot something more than 1 yard away. This applies to all combat rolls made at greater than a Reach 1. Also apply this penalty on all skill rolls for delicate tasks. Ignore this penalty if you have Nictating Membrane 2+ (½ penalty for Nictating Membrane level 1), Aquatic, a good dive mask (½ penalty for a cheap mask) or if your head is above water.
	Combat often occurs in three-dimensions, with combatants swimming below and above each other. This can become quite confusing, especially for non-aquatic or non-amphibious participants. In effect you may attempt to flank an opponent regardless of facing if you are at least one hex above or below your target. This is similar to a run-around-attack, and gives the opponent the standard -2 to Active Defenses for being flanked. In order to take advantage of your position, you must roll a quick contest of Aquabatics, if you win you are treated as flanking your opponent for this turn only. Absolute Direction gives you a +3 in this Quick Contest, while 3D Spatial Sense gives a +5 bonus. Those with Peripheral Vision can only be flanked if they actually fail their roll, while those with 360 Degree Vision can still Dodge without penalty even on a failed roll. You may substitute a Body Sense roll for an Aquabatics roll if you have Swimming at HT level (or are allowed to substitute HT for swimming). You may make a flanking roll if you are above someone walking along the bottom, however they may substitute their DX for the Aquabatics roll. Those walking along the bottom may not use Acrobatics in this contest, even if they have negative buoyancy.
	Combat underwater is very tiring. Any turn that you take any combat maneuver that includes an attack, you must make a swimming roll or lose 1 FP.  Additionally, if you are holding your breath and you are hit with an attack that Stuns you, you must make a separate HT or Breath Control roll at whatever penalty applied to the Stun roll, if you fail this HT roll you begin drowning. If combat is occurring in the water but not completely underwater (at the surface), you gain a +2 to your swimming rolls to avoid fatigue and do not need to make a separate HT roll to avoid drowning when stunned, although a critical failure on the Stun roll will still cause drowning.
	While you can’t actually suffer Knockdown while swimming, any failed Knockdown roll (or falling due to a kick or other condition) indicates awkward momentum, and increases your underwater penalties by an additional -2 to DX and Active Defenses. Take a Ready action to steady yourself, or roll a DX (at all penalties) to steady yourself as a “step”. You may replace a DX roll with an Aquabatics roll (at normal penalties) to avoid suffering a “knockdown”. Knockback is also less effective, divide final knock back by 3 if in water, although a roll versus DX is still required to avoid “knockdown” if knock back would have been 1 or more yard before the divisor.
	Amphibious and Aquatic creatures are familiar with operating in an underwater environment, thus they do not suffer the standard penalties to DX and Active Defenses. They are allowed to gain sprint bonuses and retreat as normal. They may substitute a basic HT roll for any Swimming roll. They may substitute a basic DX roll for an Aquabatics roll when attempting flank or prevent being flanked in a three-dimensional underwater combat. If they lose the quick contest, but make their roll, they may still Dodge at no penalty. Finally, they are used to working against the water and gain a +2 on all HT or Swimming rolls to avoid fatigue loss due to attacking, whether at the surface or not.

[Trachmyr]

GURPS AQUATICS, Part 4b (Rules)

Buoyancy
	In the water, things either sink or float, including creatures. Positive Buoyancy indicates that a creature floats, rising to the surface. This results in a free movement of 1 yard every turn up to the surface if the creature chooses to use it, this is in addition to any swimming. Thus a creature with a Water Move of 1 and positive buoyancy may choose to swim to the surface at the rate of 2 yards/second. However, if a creatures water move is 0, then they must always rise 1 yard/second until they reach the surface. This is a free action, and can be performed even by a stunned or paralyzed creature as long as they are not restrained, it also does not count when determining if a character may retreat. Even with Positive Buoyancy, you can still drown if you can’t keep your head out of the water, this is why swimming rolls are required. A creature that has fallen unconscious due to drowning has inhaled enough water to cancel out their Positive Buoyancy and turn it into Negative Buoyancy.
	Negative Buoyancy indicates that the creature always sinks at the rate of 1 yard/second. Sinking occurs at the end of any movement that you make, although if you have a Water Move, you can offset sinking by sacrificing one Movement. Unlike Positive Buoyancy, you do not get the option not to sink. You can choose to dive at a greater speed by adding your swim speed and Negative Buoyancy together. Negative Buoyancy does allow you to use Terrain Adaptation (Water) while completely underwater. Negative Buoyancy also affects your distance traveled while sprinting, paced swimming or covering long distances. Unless your intention is to sink at the rate of 1 yard/second, reduce your Water Move by one before calculating speed, and HT rolls to avoid fatigue for treading water are as if you were Long Distance Swimming. If this reduces your speed to 0, all you can do is tread water moving just 1/5 of a mile in good conditions in 30 minutes (1/10 a mile in rough conditions, 1/25 a mile in very rough conditions).
	Those with Positive Buoyancy can gain Negative Buoyancy by carrying Medium Encumbrance or Greater (This can vary for those with the traits Cannot Dive, Poor Diver, Floater or Ballast). Sometimes a diver will choose to do this intentionally, other times it can lead to death. At the GM’s decision, some equipment may be exempt from affecting Buoyancy if it is specifically designed to float. In fact, carrying enough Flotation equipment can cause someone with Negative Buoyancy to gain Positive Buoyancy, or someone with Positive Buoyancy to require that they must add Positive Buoyancy movement every turn. Actual lifesaving devices will do this and grant a +4 on drowning rolls.
	Creatures have Positive Buoyancy by default (until they fall unconscious from drowning). The traits Cannot Float, Landbound, and Sinker give Negative Buoyancy. The traits Cannot Dive, Poor Diver and Floater give Positive Buoyancy that always causes a creature to rise by 1 yard every turn after they move, whether they want to or not. Finally, the Perk: Ballast allows a creature to choose each turn if it has a Positive or Negative Buoyancy.


Drowning
	Unless you do not need to breathe or have a working breathing apparatus, you run the risk of drowning while in the water. Holding your breath does not protect you from the risk of drowning, although the Oxygen Storage Advantage does for as long as your internal air supply lasts. Drowning can occur under a number of conditions, when you first enter the water, on the turn after you run out of breath, or when an attack causes Stun or an incapacitating condition. Failing an attempt to rescue someone who is drowning will cause FP loss from inhaling water, but does not indicate that you begin drowning yourself.
	Whenever you enter water above your head you must make a swimming roll or begin drowning, roll a +3 if you entered the water intentionally, minus twice your encumbrance. Modifiers for build apply as normal. Failure indicates that you begin drowning. Aquatic and Amphibious creatures do not need to make a roll when they enter water.
	If you are holding your breath or using stored air from either the Oxygen Storage Advantage or from equipment like SCUBA gear, you will immediately begin drowning on the turn immediately after your air supply runs out if you are not at the surface of the water. If you reach the surface (or another source of air) before this, you do not run the risk of drowning.
	Drowning is a risk during any turn that an attack causes Stunning, or an incapacitating condition or affliction (e.g., Agony, Choking, Ecstasy). Roll an HT or Breath Control roll at the same penalty that applied to the Stunning roll, failure indicates that you begin drowning. 
	When you begin drowning, you exhale and can no longer hold your breath. You must make it to the surface or to a source of air in order to survive. When drowning, you immediately lose 1 FP and must make an HT roll to avoid being Stunned (if you are not stunned already), and a Will-5 roll to avoid becoming Panicked for as long as you continue to drown. Light a Fright Check, the Rule of 14 applies to the Will roll, any roll over 13 causes Panic. Aquatic and Amphibious creatures roll at unmodified Will to avoid becoming Panicked, but the Rule of 14 still applies.
	While stunned you must Do Nothing, you cannot retreat, although you may still defend at -4 to Active Defenses. If you have Positive Buoyancy, you may still rise to the surface by 1 yard (if also panicked, you must rise to the surface). Roll HT at the end of each turn to snap out of being Stunned. 	If you are Panicked but not stunned, you can and must move at your full Water Move including buoyancy (or your Underwater Ground Move if at the bottom of a body of water) in order to reach the closest source of air. If you reach the surface, you must spend your entire move trying to stay afloat or trying to get out of the water. This might mean grappling someone, clawing at the side of a boat, or whatever other desperate act is available. If something or someone is in your way, you must try to force your way through it or fight. If you reach a source of air other than the surface (e.g., a dropped scuba tank), you may take ready maneuvers to attempt to use it, but must make DX rolls at -4 in order to successfully accomplish a ready maneuver. While panicked you have an additional -2 to DX and combat rolls, a -4 to IQ, and an additional -2 to all Active Defenses, and cannot retreat. If you must attack someone or something, you can only take All-Out-Attack Maneuvers, and must choose either the strong or double-attack options. These penalties are in addition to the normal underwater penalties.
	If you are neither panicked nor stunned, you suffer only normal underwater skill penalties and restrictions, and are free to act as you choose. Once at the surface, you gain a +3 on swimming rolls to stop drowning. Aquatic and Amphibious creatures that reach the surface automatically stop drowning and do not need to make a swimming roll.
	While drowning you continue to lose 1 FP every turn until you reach the surface or get fresh air. Once at the surface you may make another Swimming roll, if you succeed you stop drowning. If you were also panicked, that condition ends. If you were stunned, you must continue to make HT rolls until you snap out of it, although you may tread water to avoid further drowning. If you fail the swimming roll, you lose 1 FP and continue to drown, but you manage to inhale some air as well as water as long as you remain at the surface. While at the surface you may make additional Swimming rolls to stop drowning every five seconds, losing only 1 FP per failed roll. If for any reason you sink below the surface, you begin losing 1 FP per second, and must reach the surface again to attempt another swimming roll (although you may roll again as soon as you reach the surface). If you began drowning at the surface, roll a swimming roll once every five seconds, losing 1 FP for each failure. Aquatic and Amphibious creatures that reach the surface automatically stop drowning and do not need to make a swimming roll.
	If you reach 0 FP, you must make a Will roll every turn or fall unconscious. Once unconscious, you will sink at the rate of 1 yard per second. You still are downing however, losing 1 HP and 1 FP per turn underwater or per five turns at the surface if you are still conscious. If you are not panicked, then you become so. If you reach -1 x FP, you automatically fall unconscious. Unconscious creatures due to drowning gain Negative Buoyancy, and automatically sink at 1 yard/second. Once unconscious, any rescuer will need to make a First Aid roll in addition to getting you to fresh air in order to remove the water from your lungs to save your life. Regardless of FP or HP, after four minutes without air you die, and after two minutes you must make a HT roll to avoid a permanent -1 IQ due to brain damage.