Woohoo, right up my alley! To the already excellent suggestions, I'd add carry a change of clothes (non-cotton thermal undies preferably) in a dry bag or even vacuum packed to save space. Even when the air temp is broiling, the turbulent water can can chill you from fighting it as much as the cold temperature if you go for a swim.

BTW, the best rust-inhibitor I've found is some obscure stuff called Corrosion Block made by Lear Chemical. I used to work for black pearl oyster farm right at the sea's edge and that stuff worked wonders! I get a ziploc and leave my knives and multi-tools marinating in the stuff until the next use. Hadn't seen that they have grease before; that's got potential.

http://www.corrosion-control.com/corrblock.grease.html