Dive Knife - How and what to choose

Dive Knife - How and what to choose

The knife is a critical tool to carry when going subsurface. Its primary purpose is to cut and free a diver who becomes entangled, allowing them to return immediately to the surface and change their undergarments.

The knife can be a lifesaver and requires careful consideration. So far, the author has primarily lived by the principle of "buy once, cry once," as the reader likely knows by now. However, this instance is different.

A knife is a lifesaving tool, so should you buy the best one, right? Wrong. In the author's opinion, for the purpose of SCUBA diving, it's better to buy a knife in the middle of the pack. What does that mean, and why? A middle-of-the-pack knife is one that you are willing to lose.

Imagine this scenario: you're on a dive with a knife that your dad or even your grandfather gave you. Or maybe you bought an expensive blade for $300 to $600 (which people do, and it's awesome). You find yourself entangled, manage to free yourself, but while re-sheathing the blade, it slips from your hand and falls 20 feet below you. You can see the blade resting on the bottom. It's not a decision; it's a reaction. You go for it, retrieve your blade. However, the water or tide kicks in, and you either become re-entangled or consume more air on the way up, staying in position. Additionally, you may not have realized how much time and air you burned getting out of the initial entanglement. Now you're in a situation you hadn't planned for on the surface with your buddy, and by retrieving your fancy blade, you're putting them at risk. Sadly, this situation has killed many people, not just for knives, but also for other valuables like GoPros, watches, etc.

More commonly, the sheath holding your blade comes loose, or the hilt of the blade gets stuck on something, and the knife breaks free and disappears forever, leaving you wondering how you could possibly lose it.

For this reason, the author recommends spending a sum of money on a knife that you are willing to lose.

A mindset behind diving with the equipment you have should also be brought with you whenever you go underwater. As I said before, the GoPro has certainly been a reason divers have died or had a close call. When entering the water, we all want to have fun, but ultimately, you have to think: What are you willing to die for? A $400 GoPro? A $300 knife? Absolutely not worth trading your life for. Remember, too, in the back of your mind, that if you lose one of these items in water friendly to your certification level, there is an upside. Retrieval of such items could become a fun experience for your dive buddies to attempt on a subsequent dive or the next dive group. You can even place a bounty on the item, like a 6-pack of beer or a bottle of bourbon. Your imagination is the limitation.

Where should you wear a blade? The author prefers to wear a knife on the inside of his left ankle. However, the old adage "one is none, two is one" applies here. It's easy to accidentally lose your knife when cutting through an entanglement. It's also possible that you become entangled in a way that reaching your ankle-mounted knife may not be possible or wise. It's a good idea to carry a backup in a different location. The author prefers a knife or cutting tool directly above his BC control on the hose. This spot is easily accessible and serves as a reliable reference point. Having something other than a knife provides additional options that may work better in different situations.

One important factor about a dive knife is its usage. Many divers train well and make a habit of doing drills with a backup regulator, and maybe even donning and doffing drills. But have they practiced using their knife? It is an important tool that could save your life, so it needs to be trained with. A great place to start is in a controlled environment with no waves, perhaps just sitting on the bottom at a limited depth. Carefully unsheathe and sweat your knife. Once you build comfort there, try cutting different materials you may encounter in your area, such as fishing line, netting, or lobster trap floating rope. When you're comfortable with that, move on to actual scenarios where a dive buddy wraps these materials around you in various positions. It doesn't need to be an elaborate setup; it just needs to provide some practice cutting with your different tools on different parts of your body. Some tools may work better than others. Of course, this needs to be done while being monitored by a dive buddy.

Here are a few picks that have worked well for the author:

  • The Cressi Alligator and Scissors knife: This knife is attached just above my BC control. It has a 3-inch blade that is partially serrated. Removing the small clip at the hilt transforms it into scissors, which may be useful in an engagement situation involving netting, for example. It's an easy buy at around $50.

Cressi Alligator Cutting Tool 

  • The Cressi Norge and Killer: This is a simple 4.6-inch blade that is partially serrated and has a good sheath and handle. It retails for around $50. I used a similar model for about five years, and it worked well. This knife is great for wearing on the inside of your ankle.

Cressi Norge and Killer

Cressi is a solid brand. I have never needed to use their customer service, but the price point and quality meet expectations in this category for the reasons mentioned previously.

Another great blade is the Gerber Crossriver. It's around $40, 3 inches long, and has a blunt-edged tip with about half the blade serrated. What I like most about this knife is its stealth and how the knife is retained. It has a simple, yet ingenious, plastic lever that requires only pressure to release the knife. It's easy to use and operates smoothly, even with gloves. It also has a dive-specific appearance and looks less like a weapon, which can be important when traveling internationally. Some islands frown upon blades when entering their country. This knife has a more straightforward explanation for customs due to its specific and necessary use. Unfortunately, it can only be belt or BC strap mounted and lacks a way to attach it to your ankle, which is a bummer. However, it fills the gap as a good travel knife for the aforementioned reasons.

Gerber Crossriver

A prime example of what NOT to bring on a dive is this legacy knife my father gave me, an Aqua Lung/US Divers Masters knife. It had a career as a US Army Special Forces Combat diver's tool. When he used it, it was an issued item, falling in the realm of "if I lose it, I won't die for it because the government will hopefully provide me a new one." Of course, many of us are not in this category, but it's worth noting. It's big and beefy, measuring 7 inches, and is partially serrated. It has markings on the side for measuring and a large, flat hilt, which is excellent for banging or hammering on something. Not only would it be excellent at removing a diver from an entanglement, but it would also provide a sense of security in case of encounters with large animals or other humans. It is also razor-sharp. 

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