Seac's "Sharp" diving knife has been made with capability in mind. The knife can easily be removed from the sheath and replaced again with one hand. It comes with leg/arm straps, but the sheath also fits through a weightbelt, eliminating the need for straps and placing the knife in an easy spot.
Taking care of your equipment
Rinse thoroughly with fresh water after use, wipe dry with a towel, and store in a dry place, avoiding direct exposure to sunlight and sources of heat.