how to get drinking water in sea?

there are many different desalination methods http://en.wikipedia.org/wiki/Desalination too many methods to tell you in a response so I sent you a link

You can't drink salt water and although a water filtration system could be set up to filter salt out, it requires an entire plant in a large building, so it's not the sort of thing you are likely to have on a boat, or worse, a lifeboat - since I would imagine you wouldn't go out to sea without drinking water on purpose. You would have to catch rainwater if you needed a drink. If you drank sea water, you would become dehydrated, vomit, suffer delirium and eventually your kidneys would shut down. Salt is dangerous and even fatal to the body in extremely high doses.

I know you can boil it and it will get the salt out. Not saying you can boil water at sea but that is one way to get the salt out. Also you can filter it as well. Myself personally would never ever drink sea water ever. I will bring bottles of water to sea if I had too.

well, you would not be able to get any salt out of the sea water if you were in the ocean floating there, but you will most definitely get thirsty, because since the salt is in the water, it draws water from your body, and if it goes in your mouth, it will try out you lips, and sometimes your throat. you also sweat while swimming if you didn't know that. i do not ever drink sea water myself.