Well, the main threats are deathquittos. They WILL attack you if you go near but their major priority is boat it seems, so if you manage to sail away far enough they leave you alone. Though the major threat is to be beached. It happens a lot with longboat and sometimes with karve too.

So, if you get stuck like that... well, then there's a "what are you doing step-deathquitto" type of scenario is going to happen :D