Many divers carry a knife as a tool that can be used in many circumstances-none of which include fending off sharks or crazed eels that have been genetically altered by a mad scientist. For many people, carry- ing a knife simply offers peace of mind.
Knives are typically carried by divers in case they find themselves tangled in fishing line, seaweed, or kelp. They are also used to dig or pry during a dive. Interestingly, dive knives tend to be used more frequently on land than underwater; some of the more common uses of dive knives are to tighten or loosen screws, hammer or pound items, and open oyster shells. People who spearfish also frequently use their knives to cut and prep their prey for the ride home.
A knife with a medium-length blade (4-5 inches) is typically sufficient for sport/recreational divers. A large blade will typically get in the way and become more of a nuisance than a help. A good guideline to keep in mind is the blade and grip should be almost equal in length. Therefore, a knife with a 4-5 inch blade should have a 4-5 inch grip or handle.
Dive knife blades are typically made of stainless steel, titanium, or an alloy. These options offer incredible strength and durability. They resist corrosion and maintain a sharp blade. It is important to note that even though these items are corrosion resistant, the knife blade still needs to me properly maintained, especially after a salt water dive. Blades must be rinsed in fresh water and allowed to completely dry outside of their sheathes (or left unfolded) once the dive is complete.
There are two types of knife blade: serrated and straight. Serrated blades are jagged (like a bread knife or a saw) and are very good for cutting through things like fish bones, rope, and other tough materials. Serrated blades tend to stay sharp longer than do straight blades. Straight edges are ideal for finer cutting tasks, such as fishing line. If you choose a knife with a straight edge, it is recommended to find one that is slightly curved.
Some knives offer a straight blade or a serrated blade; it is also quite common for dive knives to offer both blades at the same time. Additionally, some knives have a notch or hook in the blade that makes cutting items like fish line very simple.
Your knife's grip (or handle) should be comfortable in your hand. If you wear gloves while diving, make sure you can maintain a steady and firm hold on your knife's handle. Some grips are purely metal, while others are metal coated with rubber or a synthetic material to increase the diver's ability to safely grasp the knife.
Knife tips are either pointed or blunt. Blunt tips tend to be the better choice for recreational divers, simply because the blunt area can be used as a screwdriver and pry more safely than a pointed tip can. If you fish, a pointed tip might be the better choice because the tip can more easily butt the prey.
You have two options for knife storage- fold the knife or sheath the knife.
The first option is to use a folding knife, in which the blade folds into a groove in the handle. A folding knife is good for those who are concerned about the knife being cumbersome or a potential for snaring unwanted items (such as fish lines and kelp) because they can be stored in a BCD pocket and retrieved safely at any time. The downfall to folding knives is they aren't easy to open when wearing dive gloves or mitts.
The other option is to store your knife in a sheath. Sheathes attach to either the diver's leg, BCD pocket flap, or BCD deflator hose. Not all sheathes offer all mounting options, so make sure the sheath that comes with your knife will mount where you want it to. Some sheathes are equipped with a quick-release button; a quick-release keeps the knife secure in the sheath until the button is depressed. This keeps the knife from accidentally slipping out of the sheath at an inopportune time.
If you are traveling by air to a dive destination, do not pack your dive knife in your carry-on luggage! Airport security will confiscate your knife. Instead, pack your knife in your checked luggage.
Another option to taking a knife on vacation is taking a line cutter, which is a less ominous-looking tool that can perform many of the same tasks that a knife can.
Does your dive knife lack a holster? This neoprene Holster comfortably wraps around your leg, conveniently housing your knife in a rugged & safe place.
The last thing you want to do is find out on the beach or dive boat that something is wrong with your gear, and not have a way to fix the problem. By carrying a save-a-dive kit, you can still safely enjoy your dive or snorkeling adventure just like you planned.