[carsonbaker]

This is controversial, but Alain Bombard (http://www.nytimes.com/2005/07/24/obituaries/24bombard.html) sailed across the Atlantic, surviving on seawater, fluids from fish, and plankton.

Seems like you might be able to drink a little seawater, but not too much -- maybe a pint a day at the most. Natural History magazine has a great article on this:

http://naturalhistorymag.com/picks-from-the-past/181950/thir...