The knife below has seen a lot of exposure to water. It was a kitchen knife for years, but I could never convince my wife that it should be cleaned by hand; it continually found itself being cleaned in the dishwasher, so I finally retired it (with no rust spots evident). I wouldn't recommend this knife for kayak use, though, since it has no hole for a thong.
Have you considered
MISSION knives? Mission uses totally corrosion-proof titanium. Their knives have survived soaking in seawater for over four years without a hint of corrosion. The blades are cleaned in concentrated hydrochloric acid ... and you probably know that titanium is used by the Navy Seals and Explosive Ordinance Disposal guys.