Maybe a good knife for use in wet conditions may be the answer to your husbands gift.
A Benchmade 100SH20 might be a good choice:

100SH20

High visability, Blunt tipped, almost rust proof steel, serrated so it cuts line/cord/rope/webbing with ease, benchmade quality, ect. If he carries a regular folder this would be a good addition for his PFD, especially if he constantly wears one (with the inflatable style PFD would be a good gift too, I find them more comfortable so I wear them more often, which means I have a better chance).