content: Seawater has dissolved salt, which means molecular-level filters are needed. Instead boil the seawater and use your socks (or preferably something cleaner and not soaked in sweat) to collect the water vapor. Or, even better, use a plastic tarp to collect the water vapor and let it drip into a separate container. If you're not near the ocean you can crush leaves or cacti and heat that (and again collect the water vapor) to get water that probably won't kill you.  about how salinated is sea water ?  http://www.answers.com/Q/What_is_the_salinity_of_the_pacific_ocean  at what level is it deadly?  Greater than 9 grams per liter will make you more thirsty. (so you'll drink more until you die) Less will tend to quench your thirst. You do need some salt to survive, more if you're sweating. fun fact: soda is loaded with salt. you don't taste it because of the massive load of sugar. They do it so people will drink more soda.