Nowadays you can use a desalination pump - but lots of effort for very little water.
When I was doing survival course's (blech) a desalinator, small floatable ring, fill with salt water, evaporates leaving salt behind, fresh water drains off for drinking, was recommened - but you need a couple for each person.
Fish eye's are full of liquid, turtle blood at a pinch, alway make sure you have a nylon tarp 6' x 3' to catch water and something to put it in when you catch it.
Basically you keep all this stuff in a Ditch Bag - along with other basics and grab it when the boat/ship/whatever goes down - give me the jungle/bush/veldt any day....