Most Leatherman are 440 Stainless, though not as corrosion resistant as 300 or 330 stainless, it is better then a carbon steal or some other low chromium alloys. I would say just a rise in water and then try with a cloth would do sufficent. When I dove in Okinawa I would just rinse my equipment, incluiding a 440 stainless dive knife. So I would say nothing more invasive then just a rinse in fresh water. A shot of WD-40 never hurts either.
cheers