Underwater knife

In dangerous situations, under severe stress, when there is no time and other life-saving appliances, the knife is primarily required for accessibility and reliability. It should hold tightly in its scabbard, but be reached quickly with one hand. If the knife is held by some fixing elements, it is necessary that they are not too small even for thick gloves and not so strong that in extreme situations or panic it was impossible to remove the blade with a simple jerk, without preliminary manipulations. Ideal sheath, mounted anywhere in the body and equipment at any angle.

One of the main tasks of a diving knife is to quickly cut fishing lines , nets and other rope-rope products. For this, it is often made double-edged, and at least part of the blade is equipped with a serrator . Sometimes on the blade there is also a hook sharpened from the inside to capture ropes or gear.

The knife of the submariner is often his only tool and is forced to not only cut, but also to replace many other devices urgently. The blade is good thick, with a large margin of safety: it must withstand the rough work of a wedge or lever. In some models, the tip of the blade is cut; such a knife can also be used as a chisel or screwdriver; it is also less traumatic during rescue operations. As a weapon, a knife under water is used very rarely ^[1] .

Sea animals that can attack scuba divers - fish ( sharks , moray eels , barracudas , stingrays , catfish , marlin , groupers , etc.), seals , walruses , sea ​​snakes , large cephalopods are usually protected by thick skin, thick scales or thick subcutaneous fat interlayer. Therefore, for effective protection, the tip of the underwater knife must be very sharp and have a shape that facilitates the passage of the knife when it strikes through a dense structure. Stiletto knives or tanto knives are preferable.

In wet, thick gloves, it is convenient and safe to work with a knife with a pronounced guard or finger rest, with a large, embossed, rough handle. But a handle that is too thick does not allow the knife to fit snugly against the body when worn, it is easier to cling to algae, nets and other underwater objects.

A handle with a metal ending can give signals far audible in the water, striking the cylinder , the hull of the vessel, etc., and also use it as a hammer. Some blades are marked with measuring markings. This is all the more valuable because the distances appear to be 1.33 times greater in water than in air (due to the difference in refractive indices ), and it is difficult to correctly evaluate them by eye.

A knife dropped under water can drown at a depth or burrow into the bottom sediments, where it is difficult to find. Therefore, underwater knives with neutral buoyancy are practical: they hang in the water column or stop at the bottom at the tip of the blade. Many have a bright color or lanyard .

Salty sea ​​water destroys many materials that are resistant to air. This must be taken into account when choosing materials for the knife itself and its fastening elements. The blade must be made of special alloyed stainless steels with a high content of molybdenum, chromium and vanadium, preferably antimagnetic. Dampness in the scabbard is undesirable, it is better to make them from non-absorbent materials and provide openings for the drain and quick drying.

Professional divers and scuba divers traditionally use long, massive, rather blunt-edged blades that can quickly cut ropes and act as a coarse, fracture-resistant tool. The tasks of special forces are more likely to correspond to forms close to combat . In general, such models are relatively conservative compared to sports ones. A classic used today is a diver’s knife with a steel blade screwed into a brass sheath pipe. Recently, professionals often use folding multifunctional tools along with the main blade.

Many modern underwater knives are shorter than the old, classic ones. Blades rarely make longer than 15 cm, more and more light, short-blade, even folding models are produced. Firstly, as constantly improving materials and aggressive sharpening of the blades can achieve good cutting properties even with a short length. Secondly, a long and heavy knife is not always convenient; there are few options for its comfortable fastening. Thirdly, diving is more widespread today than in the middle of the 20th century and earlier, and the percentage of enthusiasts in it has increased. Spending only a few hours a year under water as a sport or hobby, many do not see the point of acquiring expensive and not always convenient professional equipment.

For amateur divers, an underwater knife is an emergency tool rather than everyday work. The modern assortment is guided by the variety of ideas about such cases. It presents as many models of the classic profile, as well as a whole class of so-called rescue tools. They are designed primarily for the rapid dissection of ropes, nets, lines, for comfortable carrying, while being relatively safe and unsuitable for military operations. Usually these are sharpened hooks of various shapes and designs. They can be equipped with additional cutting edges, saws, grabs, screwdrivers, carbines, impact elements for breaking glass, etc. Some models are more likely to be multi-functional cutters than classic knives.

Compared with professionals, amateurs in their choice are often guided by the price, originality and attractiveness of the design, the presence of additional functions, as well as advertising. The term tactical (English tactical ), often used by manufacturers and sellers, in relation to knives should be understood more as universal , moreover, it usually implies some suitability of such knives for use in combat situations. As a rule, these are small knives and daggers of aggressive design, often folding. Full-size, specialized combat knives are usually not called tactical.

Many products for amateurs and athletes are distinguished by catchy colors in order to facilitate their search in case of loss and increase visibility during search and rescue operations, while professional, especially combat models are designed in camouflage tones, and blades are equipped with anti-reflective coatings. Universal land models are also purchased, more or less suitable for use in water.

A perfectly positioned knife can be quickly reached in any situation and with any hand.

A common shin mount is suitable for long, heavy products, but not quite well: if you get really entangled in the net, stuck or caught, you can’t reach the knife. The same goes for placement on the back. Suspension on the cargo belt is dangerous because, along with the emergency ballast , the knife will be lost, moreover, in a situation where it may be necessary.

Mounting on the shoulder harness or in the abdomen is more successful, and if the size and design of the knife allow it, on the forearm or on the inflator hose.

For divers diving with heavy-diving equipment (three-bolt, twelve-bolt), the knife is usually located on the belt.

The vast majority of underwater knives are traditionally made of steel . It is inexpensive, very durable and holds sharpening well, but its base - iron - quickly rusts in sea water. It is necessary to use particularly stable, high-alloy steel grades and protective coatings, but even they do not guarantee complete protection against rust. It is recommended to wash steel knives with fresh water, dry and lubricate after each immersion, sometimes disassemble and clean, if the design allows. Corrosion destroys a thin cutting edge, so steel blades in seawater lose their sharpness over time. They also cause deviations near magnetic compasses and are very dangerous when mines are cleared with a magnetic fuse . However, they are preferred if you have to cut a lot with a knife. Steel for underwater knives usually does not harden to the limit of hardness, as brittleness also grows with hardness.

Blades made of titanium (more precisely, made of titanium alloys) are very lightweight, quite durable, do not magnetize, do not require corrosion protection or constant care, so they are often used by professional scuba divers and combat swimmers. The disadvantages of such knives are the high price and relative softness of titanium, which, compared with high-quality steel, quickly dies when cutting.

Ceramic blades do not rust, do not magnetize, and excellently hold sharpening. However, due to their fragility, they are not quite suitable for submariners.

Network entanglement is one of the typical cases. This constantly happens when amateur scuba divers dive on wrecks, which are often entangled in fishing nets. Diving in caves, every now and then are entangled in the elements of equipment in the lines (the so-called "Ariadne threads"). Then use special knives or sling cutters. Scuba divers, rescuers associated with the surface of the running line (for example, when dead bodies are pulled out), are sometimes hooked by him for something. Then, it happens, the hodovik also has to be cut. The list of applications can be continued, but I think the above mentioned already shows how important an underwater knife is sometimes to save a life. ^[2] ( Jens Hilbert )

The dangers of networks are often underestimated. Their varieties of colorless nylon are poorly distinguishable in water even near, in good light. Networks may come off and be carried far away from the installation sites. Russian forums of anglers and underwater hunters often mention poaching nets and hooks in rivers and lakes. Owners of yachts and motor boats have to cut winding nets or lines from the propellers and underwater parts of the vessel. Fighting swimmers use knives to defuse sea ​​mines and other special operations, as well as directly for defense or attack. Knives are widely used when diving.

The following companies are involved in the production of diving knives, spearfishing and combat diving knives:

• OceanPro (USA)
• Katz (USA)
• "CRKT" (USA)
• Gerber (USA)
• Smith & Wesson (USA)
• "Extrema Ratio" (Italy)
• TUSA (South Korea)
• Sargan (Russia)
• SARO (Russia)
• Melita (Russia)

• Scout Knife
• Sling cutter
• Knife (diving)

1. ↑ Zanin V. Yu., Malyuzenko N.N., Chebykin O.V .: Equipment for an underwater swimmer. St. Petersburg, 2003, p. 40
2. ↑ From an interview with Jens Hilbert, a martial swimmer, instructor and German deep diving champion: http://www.messer-portal.com/basiswissen/messerwissen/spezialmesser/tauchermesser