I would use a Boye Folding knife. A dedicated boating knife that will never rust, as it is made from cobalt and titanium. It is also non-magnetic, so it won't affect a compass. I have one, and like it, though I haven't been boating in years (crazy, I know). They are expensive, though. They also make a fixed blade version, if that is your preference.
Oh, I forgot to add that I also have a 639 Fieldmate. Bought it new around 1988, when I was in the Navy. But it is a closet knife and I've never used it. I would choose the Boye knife first, for real world use.