Royal Canadian Navy divers used diving knives like this to help them perform tasks underwater, including the inspection of vessels and salvage operations.

The knife (top) has a wooden handle and is threaded just below the grip so that it can be screwed into the sheath (bottom) to prevent it from slipping out and getting lost. One edge of the blade (lower) is serrated to help cut rope and other materials. The sheath is made of brass to resist corrosion, and is cylindrical to accommodate the rotation of the knife blade as the knife is screwed into place.

Knife, Diving
CWM 19900076-590