Dive knife. Either the UK Fusilier, or the smaller UK Remora. Both work great in ocean diving. With any knife that's going to get wet a lot, especially in salt water, coat with a dab of food grade silicone grease.
Never use a lanyard.
Ditto a neck knife. Not good for diving, kayaking, canoeing, etc. Better to attach the knife to your vest.
Never use a lanyard.
Ditto a neck knife. Not good for diving, kayaking, canoeing, etc. Better to attach the knife to your vest.