[ericthered]

comments on the races I find the most interesting first:

On Sessiles:

• +2 IQ is a pretty big deal, based on just how broad Gurps IQ is. It benefits social skills, academic skills, and crafting skills like fishing. It also effects will. I find racial templates are generally better if the broad bonus is traded in for a more specific one, and if they really call for additional IQ, +1 is usually enough.
• The extra arms of the sessiles could use some work. In Gurps we buy the effect, not the description. I find most tentacled Aliens shouldn't have an arm for each tentacle: the exception is if they really are that good at grappling. The sessiles are obviously not: you came up with a custom limitation to indicate they can't grapple with all of their arms at once. This would also indicate that they don't really have flexible. so They might just have extra arms 2 (short -50%) [10], arms (short -50%) [-10].
• Which brings up a build issue: you need to modify the existing arms as well as the extra ones.
• The seven extra mouths is an interesting case: the creature has them, and while they don't breathe, they do all bit and speak... though it seems they bite poorly. I feel like this should have a solution, but I'm not sure what it is. I certainly wouldn't want to pay 21 points for the ability to speak in 8 different voices if I somehow acquire that many copies of compartmentalized mind.
• Invertebrate is a weird combination with Sessile. Sessile kind of makes invertebrate irrelevant.

On Triphibians:

• Is absolute direction a necessary part of the build? I can see it as a fun little add on, but the sort of thing that fades when you live in a civilization. Changing it to something that is common but not required would be nice.
• Shouldn't Triphibians have one arm, if they're just picking things up in their mouths?
• They're very mobile. You've refference waterfowl, but they can run faster, swim faster, dive deeper, and fly just as well. You could remove pressure support and enhanced move (water), and buy down their ground move by 1 (I usually do that or more for creatures that crawl) and you'd still have a very capable mover.
• Giving the whole race curious and impulsive is very strong and potentially crippling. I'm drop that to quirks, and stick the full version in "common traits". Same for Chummy.