A vital safety tool for underwater adventure, a solid dive knife is a must-have for your dive kit. Here’s what you need to know to get the best one.
Dive knives are specialized edged tool that is made for people who spend time in the water. This seems like a wide definition, but water sports are a huge series of pastimes as well as a profession for millions of people across the world.
Diving, be it scuba or free diving, is inherently dangerous and rife with hazards, including the gear you may have on your person. The dive knife varies in profile and material, but in the end, it is a tool that can be relied on to remove yourself or another from a tangle of floating netting, a strap caught on an underwater branch, or to evacuate a struggling diver from their tank.
The dive knife is more than a rescue tool, though. In the alien environment that exists underwater it is a lifeline to the surface and a last resort in the worst situations.
Dive Knife Construction
In the course of use, most real-world knives are going to get wet, however, but are not meant to stay wet for extended periods. Getting caught in a rainstorm or left outside by the fire are things that happen, but being submerged in saltwater for weeks on end would destroy most knives as well as erode and damage handles and sheaths. Leather is not found on serious dive knives, nor is wood or carbon steel. These materials are simply eaten away by salt water and are also easily damaged in fresh water.
Dive knives are typically constructed using corrosion-resistant materials and have handles molded directly to them. The idea is to reduce the number of areas where water can enter, making the knives last longer. Very few materials are absolutely corrosion-proof, but they can be made resistant to the point where they won’t degrade for years or decades, sometimes even the lifetime of the owner.
Dive knives are also less rugged for on-land work. Most of the blades of dive knives are thin, sitting in the .12- to .16-inch range, making them unsuitable for heavy use on wood or for camp work. In the water, you’re likely not going to baton logs, so the thickness of the stock is unimportant except for its ability to cut through materials.
Nylon and plastic are the main prey of dive knives, it is the main material for everything from rope to fishing nets and is the basis of most straps on a diver’s gear. It is not that there is only one used in this sense, rather it is that the vast majority of materials a dive knife needs to cut are man-made and are of a relatively normative quality.
Dive Knife Features
When looking at the must-have features on dive knives, one finds that there is no specific answer.
As noted above, the general concept of a dive knife is to cut through maritime-related cordage. The secondary functions are almost irrelevant to this, self-defense isn’t even a tertiary topic considering that shark attacks are exceedingly rare. Natural obstacles like kelp can hang a diver up, and this is perhaps the only naturally occurring material dive knives are commonly used on.
A Sharp edge is the knife’s the main feature and is simply a must—no questions asked. Serration is very ideal on a whole edge and is truly better for cutting rope or nets over a plain edge. A plain edge is great as well, but for cuts that don’t necessitate a sawing motion. Glass breakers in the pommel, paracord wraps, and other features aren’t necessary and may even get in the way. Simplicity is paramount in a dive knife, you should never have to guess where your edges are when working in poor lighting conditions with limited oxygen.
Dive Knife Designs
Popular profiles vary, usually by tip profile. Some divers prefer a Bowie style with a sharp, aggressive tip. This is nice for fine work, especially on primary knives that may be used for harvesting oysters and other such tasks.
The other main category is blunted or flat-tip knives. These have a tip similar to pry knives in that they have an abbreviated, square-edged tip. They can also be used for various purposes, but their main advantage is that they can be slipped under straps on a diver’s body safely without risking stabbing or lacerating them. Injuries can still occur, but the serious risk is reduced.
Best Dive Knife Size
There is a general limit to the effectiveness of a knife used underwater. Thrusts and slashes are slowed down by the resistance of the water itself, and you tire much easier than on land. As a result, there is certainly too big of a knife, with the lower limit being around 3 inches, or just enough to get under most straps and tie-downs.
The handle should not be too small, however. Many of these designs have a dagger-like overall profile, though, a good scuba or dive knife should not have a dagger handle. You need to know where the edge is by indexing the handle. As a result, a beefy handle and 3- to 5-inch blade are what you want to look for a dive knife.
Steel Vs Titanium Dive Knives
Titanium is hands-down the better material for use on dive knives from a corrosion perspective. Titanium, however, doesn’t hold an edge as well as steel, but when sharp it cuts maritime materials just as well. Sharpness is a main benefit of steel, though even the best steel can experience corrosion over extended saltwater exposure.
Some divers swear by steel, others by titanium, and this seems to be an ongoing debate. Steel coatings are better and better these days, and some steel knives are available with a titanium coating. Again, the benefits are largely subjective, most users won’t notice a difference with regular maintenance. Like all hobbies, the vast majority of conjecture takes place in the 1-percent of professional or constant participants.
Best Dive Knives At All Price Points
Benchmade H20 Fixed Dive Knife
Benchmade is well known for some incredible and durable products. The H2O fixed dive knife is an example of this.
Designed for military use, the knife carries a national stocking number (NSN) and is exceptionally well laid out for its purpose. Interestingly, this knife has features that are not necessarily in line with what many of the experts say are best.
For starters, it has a relatively simple grip that lacks the excessive texturing found on many other dive knives. The blade is also made of steel, which stands in the face of those that say titanium is a must-have for saltwater exposure. This is not to say that it is the end-all, be-all knife for use in the water.
While the military has picked some good products in the past, it can’t be said that they are correct every time. This knife is a great starting point at a medium price, you get a blunted tip, strap cutter and serration, as well as a generous lanyard loop. The sheath, while relatively basic, can be adapted to many types of carry depending on what you’re doing in the water.
Hogue Knives EX-FO2 Dive Knife
As a general purpose outdoor knife, Hogue has a winner in the EX-FO2. This knife is right in the “perfect size” range for a dive knife, however, it has some features that make it both spot-on and a bit questionable at the same time.
Looking at the positive angle first, this knife is very well laid out and has a nicely shaped handle that has positive reviews for water use. The sheath setup is also excellent, it comes ready for attachment to your arm or leg with a padded backer. This is a knife that has multiple end uses. It is sort of a hybrid of a fishing knife and bushcrafter in that it has a stout blade that can be great for filleting but strong enough for general use.
This knife is available as listed with only a tanto point or clip point. For general use this is fine, however, it can be a liability diving. A completely sharp tip is a negative to some, the risk of puncture or personal injury is potentially much higher as opposed to a blunted point.
Fox Knives Tenko Military II Dive Knife
Fox Knives is an Italian company that makes high-quality products at reasonable prices. The author has used Fox products for quite some time, and all of them have held up very well.
Their dive knife is feature-rich, almost to a fault. The knife is double-edged, one serrated and the other clean. The rear part of the spine has a cord hook directly behind the separation. Unlike the others on this list, the Fox knife has a full cross guard that allows you to choke up on the blade for high-impact puncturing or slashing. This knife has a very fine tip, and while it is military-themed, this tip is a bit too aggressive for rescue work or freeing even yourself from a tangle. A bonus of this knife is that it has a full rubber handle as opposed to textured plastic.
Spyderco Salt Fish Hunter
Unlike the rest of the names on this list, the Fish Hunter is exactly that, a hunting knife. While many of these knives can be used for fishing in general, Spyderco’s product here is expressly made with the intent to be used as a companion for spearfishing and adventurous free divers. This is a specially designed product, and shouldn’t be confused with other dive knives or dedicated scuba knives.
The blade is hollow ground and comes to a very aggressive tip. Serration starts just after the tip and continues to the handle. Many fish are surprisingly thick-skinned and are quite difficult to kill, this knife makes it relatively effortless and the serration allows for quick cuts through even the thickest scales.
While this knife of course can be used to aid in an emergency, it would likely be best to bring a dedicated, blunted rescue tool as well. Spyderco designed their Salt line to fit this bill, and you can find products that are geared towards rescue and escape as well in their lineup.
Extrema Ratio Ultramarine
By far the most expensive dive knife on this list, and perhaps the production market, the Italian-made Extrema Ratio Ultramarine is a purpose-built, do-all dive knife. Curiously, for being so costly, it is not made of titanium or another material less subject to corrosion.
Much like the Benchmade H2O, it is a steel knife. The Ultramarine is double-edged, one clean, and one serrated, and it includes a strap cutter and wrapped handle for a very sure grip underwater. The covering is removable. The knife comes with a functional sheath and case.
You may ask yourself just what you get in terms of the extra hundreds of dollars and, well, that is something only you can know. The possibility of losing such an investment in the deep is not something many people want to stomach considering that many dedicated dive knives are less than $100. This is one serious knife for perhaps the most serious users.
Aqua Lung Argonaut Blunt-Tip Titanium
Aqua Lung has a real winner here with the Argonaut. This knife is available as a blunt tip, as well as what they call a Spartan tip, which has a leaf-shaped, pointed profile. For our purposes, here, the blunt-tip version is the knife that we are going to be looking at.
As a scuba knife, it is perfectly suited for the task. The squared, blunt tip profile allows it to easily get underneath any strap, and, depending on what you need to cut, it has a sharp plain edge and a serrated edge. The knife is made of titanium, which is a choice for many people that spend time in the water. This material is far less vulnerable to corrosion and is also quite light. It is relatively thin for its end use at .15 inch, so prying is not on the menu.
This knife comes with a dedicated leg or arm sheath and is moderately affordable at around $200 retail. The handle is simply wrapped in cord, which somebody finds to be a detriment over a high texture Nylon handle.
Promate Snorkel SCUBA Knife Titanium
The Snorkel is an affordable, multi-function, titanium knife that is very well thought out. It has a plain main edge and a serrated spine with a cord cutter. While it is substantially less expensive than the others on this list, it boasts very high reviews across the board and is by all accounts the standard, by which all scuba knives are judged. If it does not perform as well as this affordable model, it probably is not going to perform at all.
The Snorkel is available as a blunt tip, as well as a very aggressive Bowie profile. Depending on what you’re going to do with it, the former is more functional for general use, while the latter is going to give you an advantage if you are spearfishing or free diving. Because they are half the price or less than almost everything on this list, you can get one of each and still have cash in hand. These knives are available in different colors to suit your interest and come with a functional sheath setup for use in the water.
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