I remember watching some History Channel program on the sinking of the Titanic quite a while ago. The program was about "what if's" if I remember correctly. Anyway, one idea that came out was that many more people could've been saved if the captain had used the thousands of doors that the Titanic had since there weren't enough life boats for everyone but they did have the luxury of time.

Set up some sort of containment ring on the ocean surface...I forget how they suggested it...then throw as many doors as possible into the ring to create a rudimentary floating platform. Not as good as a proper boat, of course, but it does seem to provide buoyancy and helps keep more of your body out of the frigid ocean water. Don't know how feasible this idea really is in real life, but you're not the first person to wonder if doors could be useful in this capacity.