Yes, abloy would be good as mentioned, but I would actually lean towards Squire as Illusion said because their locks are specifically designed to be used underwater, and in a salt underwater environment I might add, which is much more corrosive than fresh water. They are 'supposedly' (I remember hearing this but can't verify it) used by the British Navy and Oil Rigs in the North Sea to lock things up underwater.
http://www.squirelocks.co.uk/html/oldeng.htm
"Can be used in extreme harsh environments such as sand, on the ocean floor, exposed landscapes, forests and mud."
And if want something a bit more secure, you could go for one of their 6-lever padlocks like this:
http://www.squirelocks.co.uk/html/profhs1.htm"I think people should be free to engage in any sexual practices they choose; they should draw the line at goats though."
Elton John
