An excellent account of just such a survival is Steve Callahan's 76 day survival and recounted in "Adrift." I think most folks here are familiar with it. If not, I highly recommend it.

For the super short version, read his "5 Realities of Being Lost at Sea" here:
http://www.cracked.com/article_21145_5-things-i-learned-about-survival-while-i-was-lost-at-sea.html