Mares Neutron Diving Knife

The Mares Neutron is a compact dive knife: 137mm end to end, a 440 stainless steel blade under a PVD coating, and a Cordura sheath on belt loops. The spec rows list a straight edge, a serrated edge and a separate line cutter on the one small tool, with a screwdriver and a bottle opener on top of that. Mares built it on the pattern of its own Maximus knife, and it suits recreational divers who want a cutting tool that rides on their kit without getting in the way.

Who this suits

This is the knife for divers who keep leaving the knife at home because it snags on everything. Mares files it under the compact size category, and the whole thing is 137mm long, so it sits on a waist strap or a calf without you thinking about it until you need it.

It also suits divers who split their year between the sea and a lake or quarry. Mares lists the Neutron as suitable for both saltwater and freshwater diving, and the coated blade is the reason it copes with the first of those.

Skip it if you want a full-grip knife for heavy work, where a longer handle and more blade behind the cut do the job better. Skip it too if the length of the cutting edge is what decides your purchase, because Mares publishes the total length only. Blade length and thickness are not in the spec rows, so ask the retailer.

137mm, and what that costs you

The 137mm figure is the whole knife, handle included, which means the working edge is a good deal shorter than the number suggests. That is the honest trade in a compact knife and it is worth having straight before you buy.

What you get back is a knife you will actually be wearing. A small blade mounts flat on a BC strap or a calf, stays out of the way through a doorway or a kelp line, and does not catch on a hose. A knife you left on the boat because it was bulky cuts nothing. What you give up is force. You can saw through a fouled line with this, but you are working with your fingers close to the job rather than standing off from it.

Three ways to cut, on one tool

The Neutron carries a straight edge, a serrated edge and a line cutter, and each answers a different problem in the water.

The straight edge gives you a controlled cut through soft line or webbing where you want to see exactly where the blade goes. The serrated edge saws through braided rope, netting and anything fibrous that a plain edge would skid across. The line cutter is the one that matters when you are the thing that is tangled: it is a shrouded notch you hook over the line and pull, so nothing exposed goes near your hose, your suit or your hand while you free yourself.

Carrying all three on one compact tool is the point of this knife. You are not deciding between a blade and a cutter on the surface and finding out at depth that you chose wrong.

440 stainless with a PVD coating

The blade is 440 stainless steel, the standard grade for dive knives because it takes and holds a usable edge while resisting rust. Resisting is the operative word. Stainless still corrodes if you leave it wet and salty.

The PVD coating is the answer to that. Physical vapour deposition bonds a thin, hard layer onto the metal, and it is what Mares points to for the knife's corrosion resistance. On a compact knife that spends its life in a damp sheath strapped to your leg, that layer earns its keep. Rinse it in fresh water after a salt dive anyway.

Carrying it, and the topside extras

The sheath is Cordura with belt loops. Cordura is a woven nylon that shrugs off abrasion, which is what a sheath needs more than anything else, and belt loops keep the mounting simple: run a strap through, done, with no proprietary clip to snap or lose.

The screwdriver and the bottle opener are not why you buy a safety tool, but they are the reason it stays in the bag. Fin straps, a loose battery cover on a torch, a hose clamp: a screwdriver on your leg beats one in the boat locker.

The bottom line

The Neutron is a good compact answer for recreational diving: three cutting options including a proper line cutter, a coated 440 stainless blade rated for salt and fresh water, and a size small enough that you will actually carry it. It is not a heavy-duty knife, and 137mm total length means less blade and less force behind the cut than a full-size tool. Mares also publishes no blade length, thickness or weight, so if those numbers decide it for you, get them from the retailer before you order.

Specifications