so, with the razor coast campaign coming up, i have a couple of ideas, like a handheld cannon, that sort of looks like this:
it would do 2d10 damage, and lower your DEX modifier by two. it would, however, require a +2 str mod to operate and reload. it is a masterwork weapon and requires a full round to reload.
with quick reload, it counts as a move action.
my second idea, is perhaps randomized shark attacks while swimming in the water, governed by a roll of the d20 every 25 feet travelled in the water.