Water is life. I will keep saying it, and you should let it soak in and commit it to memory. That said, when you are in a survival scenario, you have two issues regarding water: finding it, and making it drinkable.
This is hard enough in jungle, forest, or desert settings, but consider one other; the ocean. Truly frustrating, all that water, and you can’t drink it. You might be out for a deep sea fishing expedition, and have mechanical/electrical/fuel issues. Perhaps you find yourself on stuck on a deserted beach. Long story short, you’re stuck, and you need water. Salt water is a no-go, for a lot of reasons, so what to do? If you don’t have a desalination system on your boat, you may need to build one of these, a distillation system.
Granted, building one will require some specific materials, but if you think smart, and plan ahead it won’t be that hard. Packing stainless steel canteens (Klean Kanteen, for example), and perhaps some copper tubing (you could perhaps use another type of tubing…need to research this more) puts you ahead of the game.
Remember, survival is a thinking man’s game. If you consider your environment, and situations that may arise should things go sideways, you can plan/pack accordingly and ease your suffering.
Keep doing the stuff!
Ne te quaesiveris extra