I'm not sure it really will like a saltwater environment or it's waterproof. Like you said, the consequences of a short or control problem can be a mild irritation or a lot worse. You certainly shouldn't leave the windlass switch on the breaker on unless you're on top of what you're doing and need the windlass. I'd tend to take the batteries out when you weren't using the remote.

HERE'S the Loffrans wireless. I'm assuming they have something similar, or it would work for you. http://ca.binnacle.com/Windlass-Accessories/c34/p8675/LOFRANS-GALAXY-303-WIRELESS-WINDLASS-REMOTE-CONTROL/product_info.html

There are all kinds of "BAD" stories about what happens when you connect high power winches and put soft tissue in harm's way. Then there are issues with having a hard (over)load on the winch.

Anyway, I positioned my foot switches to try to minimize the likelihood of something bad happening -- still, you can stretch yourself into a problem.