Leatherman or Gerber, both are good but they are tools not just knives. My hands down all time fav for a boat knife is a Victornox (Swiss army folks) 4 inch searated parring knife. Razor sharp, hold a decent edge, cost five bucks so they are disposable and they have a varaity of carry options including a hard plastic sheath that works great around your neck and a slip on nylon belt sheath as well as tucking them into nooks and crannies about the boat. I issued one brand new to all new deckhands on my Comm fish boat with strict instructions that it was never to be used except to cut someone out of the gear. Had to stay on them all the time as the knife was so handy. I want a brand new blade if someone get tangled and goes over the side.
I have bought 100 or more over the years. Found at any comm fish store.