Swept Away on an Unusual Island

[Cornelius]

So last night I was jotting down ideas for a new set of adventures on my Journal of Adventures that will never be played (TM).

The idea is about a group of friends that are shipwrecked on a Mediterranean island by a sudden storm.

When they recover and start exploring the beach on which they have landed, they quickly discover that the island is inhabited by fantasy creatures not very friendly (scratch that: straight hostile).

So, to cut a long story short, the whole catch is that the characters are stranded on a fantasy world (Mediterranean late bronze age) and have to find a way out, before the Olympian gods takes notice and decide to have some fun with them. It's a way to recycle a bunch of old fantasy adventures with a new souse (just like you do with yesterday's leftovers). Nothing really original or new.

My problem is that I don't know how to realistically give the characters enough knowledge of hand to hand combat and eventually magic to survive, without resorting to "corny" tricks like gaining such knowledge suddenly by magic.

I could circumvent the problem having the characters be soldiers. Firearms would give them a good edge, but ammo is limited. Anyway I would prefer my characters to be more average Joe.

So how would you solve this little problem?