How to Choose a Dive Knife

September 26, 2013

While Crocodile Dundee may disagree, bigger isn't always better when it comes to knives. Regardless of what they show you on TV, you will not be using your dive knife to battle sharks, giant squids, or even enemy spies. Rather, your dive knife is a tool: it'll come in handy when you're exploring a sunken wreck, cracking clams, or, worst, when you're tangled in an old fishing net at seafloor and running out of air. With the large selection of knives on the market, it may be difficult to figure out which blade is the best. This buying guide will walk you through important knife elements so you can pick out the best blade for you.


Go for either a small (2-3 inches of blade) or medium (4-5 inches) knife. Any larger, and the knife may prove too cumbersome and/or dangerous. Recreational divers only need about a 4-inch blade to help cut themselves free in the event they tangled. Blade and grip should be almost equal in length.

  • Mini Dive Knives: With 2-3 inches of blade, the minis can fit just about anywhere. You can even clamp it on your hose for quick access. Just make sure that the handle is long enough that you can get a firm grip on the knife.
  • Medium Dive Knives: This size is often the most practical. The medium-sized knife has the both heft and strength you need while ditching the ungainly length of larger blades. Medium knives can be strapped to a variety of easy-to-reach locations.

Edge and Tips

The style of your blade plays an important part in its functionality. Consider these styles for fullest safety and usefulness:

  • Straight AND Serrated: Go for a dive knife that has a dual straight and serrated edges for increased versatility. The straight edge will be good for cutting plastic, such as a line and nylon rope; the serrated edge is best suited for sawing at natural fibers like rope and kelp. Don't let yourself be caught in need of either type of blade.
  • Tip Types:
    • A blunt tip is great for prying, digging, hacking, and chiseling. With a blunt tip, you can worry less about accidents—puncturing air hoses, your wetsuit, or other divers. It's a safety-first type of blade.
    • A sharp tip is great for puncturing and cutting. They're popular amongst spearfishermen and are great for cleaning a catch. However, a sharp tip is more dangerous, and is more likely to accidentally cut or cause injury. Also, the tip can break when you are digging or chiseling, leaving you with a lesser blade. Sharp tips are generally less recommended for scuba divers.
    • A tanto tip is a hybrid of blunt and pointed. It's got an angled tip that's sharpened for cutting, often with a spot of bluntness on the very tip. It's a gentle compromise.

Blade Material

The make-up of your blade will play into its longevity. Most dive knives are made of steel, though titanium is also an option.

  • Stainless Steel: The term "stainless steel" is a misleading—they do rust, just slower than plain ol' steel, and thus will require maintenance. Rinse your knife with fresh water after each dive and to let it dry unfolded or outside of its sheath. You can also oil it or rub it with silicone.
    • Stainless steel knives often come with a series number, usually 300 or 400-series. The lower the number, the more resistant the blade is to corrosion. However, a lower number blade will lose its edge faster. A 300-series knife won't rust as fast as a 400-series knife, but the 400 will remain sharper; thus, they each require their own special attention (more cleaning vs more sharpening).
  • Titanium: Titanium dive knives are almost completely rustproof and corrosion resistant, as they contain no carbon for oxidation. A titanium dive knife holds a great edge and cuts down on maintenance time. It is lighter and more flexible than steel, thus harder to break. However, they are much pricier than their steel counterparts, and should still be maintained to keep their quality.

Sheath and Strap

When diving, your knife can be strapped to your leg or arm, or mounted to your dive belt or buoyancy compensation device (BCD). Wear the knife in a place that is most comfortable for you, within easy reach; you should be capable of drawing it with one hand. Dive knives come in either a sheath or folded:

  • Sheath: Make sure your sheath holds your knife securely, yet allows you to draw it with one hand. Most sheaths are made from plastic, which stores your knife without blunting it.
  • Folding: A folding knife tends to be smaller, lighter, and stows easier than its fixed counterpart. Most of them lock in the open position to eliminate the danger of slicing off your fingers. However, some folding knives can be difficult to open with one hand.

Though most knives come with their own strap, sometimes you'll have to purchase your strap separately. Look for straps made from double-stitched nylon, a durable fabric that can stand up to sand and rocks.

Other Features to Consider

A few more nifty knife tricks to think about are:

  • Metal handle butt: great for banging on metal surfaces to attract attention. Can also double as a hammer if the knife is large enough.
  • Line Cutting Notch: a small, sharpened groove in the knife for hooking a line and cutting it swiftly. It's an useful feature that will help free you in moments.
  • Black blade: doesn't alert marine life, but is harder to find in case you drop it. Shiny dive knives can alternatively attract and scare away marine life. In most cases, your knife will remain in your sheath.
  • Finger grips: ergonomic design for comfort and increased grip. Stops the knife from slipping.


Remember, your dive knife is never a weapon, nor should it be used to harass marine life or destroy habitats. Use your knife safely and responsibly.

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