Every diver on every dive should carry a knife. You can never be sure when the ability to quickly and easily cut through tangled line, net or rope might become a matter of life or death. Traditionally, the diver's knife is quite large and sturdy and is worn on the calf or thigh. In recent years ther has been a tendency for smaller knives to become popular and these are worn on the upper arm or the forearm.
Whichever type of diving knife is selected, there are certain requirements to be satisfied. To minimize corrosion, stainless steel is used for the blade. This type of steel is not as hard as conventional cutting steel and regular sharpening will be necessary. Although its name suggests otherwise, stainless steel can corrode - particularly the grades of stainless steel that are used for making knives - but regular cleaning and oiling will minimize the problem.
Besides a plain cutting blade, a saw edge can be quite useful for cutting through thicker ropes. The handle should be comfortable, non-slip and with a means of preventing the hand slipping down onto the blade. Most knives have handles made of hard rubber or plastic , but there are a few one-piece knives with handle and blade all of steel. Wear the knife in its sheath whenever it is not in use and make sure that it can be quickly and easily removed.
