If you aren't shredded as in ChefWide's examples... you're going to swim to where in (let's say) ten minutes?
That's about how long you've got in the North Atlantic. Longer in tropical waters, sure, but on the US - Europe routes, you will quickly reach the ambient temperature of about 50F -- being immersed in an entire frickin' ocean guarantees that. At that temp the chemical reactions we call "life" no longer take place in human beings.
Different story if you make it to a lifeboat, maybe there are several of you bundling together, you've got clothing, blankets... but the main thing is you have got to get out of that cold water or you get to be Leo DiCaprio in Titanic.