Yeah Paul pretty much nailed it. If you want to get little fancier and take a risk with different brand you can try one of these:
Spyderco Assist is a rescue knife which is going to be bit bigger than what Paul recommended. Difference is that this knife has a whistle build in (average), handle offers you more secure grip (therefore bigger knife) and it can be opened with one hand. Also you can place a rope across the hand and fold the blade close and it works are your personal rope cutter. Knife has a blunt tip so it very safe to use when your hand coordination is little off or you work close to your body.
But again it is bit bigger and different brand. My boss gave me this knife one week ago and I like it. The thing is that Assist is not a multi purpose knife. Its purpose it rescue. You can't cut food with it, use it for defense or filet fish. It should stay on your PFD or on your neck, belt etc.
Just another idea.
Matt