http://www.straightdope.com/mailbag/msaltwater.html
Quote:
Hence, if you drink too much salt water, you need to urinate more water than you drank to get rid of the excess salt, and dehydration sets in. Drinking even a little seawater starts you down a dangerous road: The more you drink, the thirstier you get.

http://www.seashellsandsuch.com/articles/canidrinkseawater.php
Quote:
So after drinking seawater, your body soon has less water in it than it did before. If you keep drinking seawater, your body gets more and more dehydrated as it pulls water from the cells to dissolve the extra salt and flush it out through your kidneys.
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Seawater is NOT nice clean, filtered water like the water that comes from your faucet. Ocean creatures die in it. And then their bodies decay. They urinate and defecate in it. Runoff from the land often contains pesticides and sometimes poorly-treated waste from cities and farms. It can carry the hepatitis virus and many others. And so on. You get the idea.

I'm not sure what the resource is on drinking a liter a day, but that would appear to make your body use more than a liter to dispose of the wastes in seawater. It may be that the liter a day presumes fresh water is freely available? Drinking only seawater at even a liter a day would appear from other online resources to mean you would deplete your stores of body fluids more quickly than not drinking at all.