I believe someone posted this link before here
http://www.watertribe.com/Magazine/ChallengeHowTo/Contents.aspx?ucPtr=WhenGodsPlay.ascxbut it is worth reposting. It primarily deals with hypothermia avoidance once wet from a sea kayakers point of view, but is applicable to anyone involved in maritime activities.
They do go into (in possibly another article) about how to attach a small backpack (hydration bladder?) to the back for more storage space.
Bill