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Diving Knife, Why Is It So Important?

Diving Knife - Main picture

If you are wondering what the diving knife is for and why it is so important, our HR and Course Director, Victor Cordoba, tells us in this article. Don’t miss it!

We have all seen in old movies the image of a diver with a huge diver knife attached to the calf, and all those who are not familiar with diving could think it is a weapon to defend against sea monsters and sharks.

I have been diving for more than 35 years and I have only had to use a diving knife once, and I assure you that it was not precisely to defend myself against any shark or sea monster. The real reason for the scuba knife divers use is very different from this conception. In my case it was in a cave passing a restriction at a depth of 102 meters. This certainly isn’t the place one would choose to test if the scuba diving knife works. Unfortunately, I was entangled on the line and there was zero visibility, but in about 15 seconds I was able to pull out the dive knife and cut the line to free myself.

The diving knife is just another diving equipment tool, that is mainly used to cut ropes or fishing nets in case of entanglement; We don´t attach it to the calf anymore and its size is much smaller than what we see in the films that I mentioned in the beginning.

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1. What is a diver’s knife used for?

A scuba Knife is designed to be carried while diving and can be used for a variety of purposes, including cutting through ropes, netting, and other materials that may become tangled or stuck while diving. It can also be used as a defensive weapon to deter marine animals. Divers’ knives are typically made of stainless steel or other corrosion-resistant materials and have a sharp, sturdy blade that can be easily accessed and deployed while underwater. They are an essential piece of diving equipment for many divers and are carried as a safety precaution in case of emergency.


2. Types Of Diving Knives

There are several types of diver’s knives and their design is intended to be useful for different purposes and environments. Here are a few common types:

Pocket scuba diving knives: these knives are small and compact. They are designed to fit in a BCD pocket or hang from the weight belt. In general, they are razor-type. That is, their blade is foldable.

Fixed-blade scuba knives: these are knives with a fixed blade and handle. They are usually with larger blades and a longer lifespan.

Dive saws: these are specialized tools that have a serrated edge and are used for cutting through hard materials, such as coral reefs or submerged debris.

Multitools: these are diving knives that have multiple functions, such as a blade, a screwdriver, and a bottle opener. They are convenient for divers who need to perform a variety of tasks while diving, as happens to commercial divers.

Line Cutter: Line cutter was developed for cave diving mainly, where one of the most frequent dangers is getting entangled in the guideline with some piece of the equipment in conditions of zero visibility and not being able to free yourself. For this situation, traditional knives are not very effective, since they are usually not too sharp and it is difficult to cut a 2- or 3-mm 0,8- 0,11-inch width nylon line with one hand in the difficult positions that sometimes you adopt in a cave or through some narrow passages.

For this reason, this tool was developed very sharp and with an indentation that can hook the line but is too narrow to accidentally cut a breathing hose, by mistake.

Imagine a diver getting hooked in a cave and trying to cut the line behind his head, severing a hose and the air supply…

The fundamental difference between a diving knife and a rope cutter lies in its shape.

The blade of the diver’s knife has a sharp and serrated part. Many also incorporate semicircular small-diameter slits for cutting-resistant threads.

Meanwhile, the rope cutters have sharper blades, which rust easily. This is because they are not stainless. In addition, being very thin, they become brittle and lose their edge, which makes it impossible to cut with them. So, if you use your scuba line cutter regularly or in harsh conditions, you may need to change it more often.

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3. How To Choose the Best Diving Knife?

When choosing a scuba diving knife, there are several factors to consider:

Size: A larger knife may be more useful in certain situations, but it will also be bulkier and harder to carry. Consider the size and weight of the knife in relation to your diving equipment and personal preference.

It’s also a good idea to choose a diving knife that is appropriate for the types of diving you will be doing. If you will be diving in areas with a lot of shipwrecks or other structures, a larger, more heavy-duty knife may be necessary. If you will mostly be diving in open water, a smaller, more lightweight knife may be sufficient.

Blade material: The blade of a diving knife should be made of a corrosion-resistant material such as stainless steel or titanium.

Stainless steel is a strong and durable material. It is also relatively inexpensive compared to titanium. However, it is heavier than titanium and more sensitive to salt water’s corrosive effects.

Titanium is a lightweight and strong material that is also highly resistant to corrosion. In addition, it is hypoallergenic, which can be important for divers with metal allergies. However, titanium is generally more expensive than stainless steel.

When choosing between a stainless steel or titanium dive knife, consider the specific needs of your diving environment and your personal preferences. Both materials have their own strengths and weaknesses, and either one can make for a good diving knife depending on the circumstances.

Blade Style: Some diving knives have a serrated edge, which can be useful for cutting through tougher materials such as ropes and netting. Others have a straight edge, which may be more suitable for precise cuts.

Mounting options: Diving knives can be mounted on a leg strap, attached to a weight belt, or carried in a pocket or sheath. Consider the most convenient and comfortable option for you.

Price: Scuba diving knives range in price from a few dollars to several hundred dollars. Consider your budget and how much you are willing to spend on a diving knife.

It’s also a good idea to read reviews and compare the features of different knives before making a decision.

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4. Diving Knife Maintenance

The diving knife or line cutter is one more element of our diving equipment and, therefore, we have to keep it in the same conditions as any other element.

Bringing a diving knife that does not cut when needed, is as if we carry nothing. Therefore, one must ensure that the diving knife or line cutter is in perfect condition. It is important:

  • to remove the knife from its sheath after each dive;
  • to rinse it thoroughly with fresh water and then dry it carefully:
  • some divers, once dry, apply a thin layer of Vaseline or silicone grease before putting it back in the sheath, which must also be dry inside.

As line cutters can easily suffer rusting and become useless, they need the same maintenance than the diving knife, but it is still inevitable that they rust, so the manufacturers of the best quality products provide replacement blades that can be changed when necessary. It is a good idea to carry some of these replacement blades in our small toolbox with basic accessories so that you can change them before a dive if needed. Some manufacturers make line cutters out of one piece of titanium that does not rust, but they are more expensive.

We already have the knife in perfect condition to use it, but where should I place it?

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5. How To Carry the Diver Knife in A Proper Way?

Obviously and going back to the movies, it should not be attached to the calf. Carrying a perfectly sharp knife is not going to do any good if during the dive we cannot reach it by a quick hand movement and efficiently. As we have said before, the calf is not the recommended place because of the bodily contortions necessary in some situations to reach the diving knife. Therefore, it is usually placed in a BCD pocket or fixed on a shoulder strap of the BCD. Some models have specific locations for the knife. Some divers use a technical diving harness, which is becoming more common, and they usually place the diving knife in a sheath on the harness waist strap. If a line cutter is used which is small and light, some divers place them on the strap or “bungees” of the dive computer.

The location of the dive knife is often a matter of personal preference, and divers should choose a location that is comfortable and allows them to easily access the scuba diving knife when needed.

In any case, scuba divers never should carry their knives in a way that could potentially hinder or restrict their movement while diving.

Remember: the most important thing is always to have easy access with both hands to be able to operate with the knife or line cutter.

If when I needed to use my diving knife it hadn’t been accessible and/or had not been sharp, someone else would probably be writing this article. And you, have you ever had to use your diving knife? Tell us on Facebook.