I bet a Utilikilt type thing wouldn't care about saltwater

As far as the compromising situations where your dinghy or fishing tackle might get overexposed, I simply wear black undies. I know, I know it's sacrilegious but if I know I'm going to be in a situation where I'll scare someone's wife or daughters (or cause a laugh fest) I'd rather just be a bit discreet. It's plenty easy to take em off later after rock climbing.