In 2023, the Alert Diver magazine from the Divers Alert Network (DAN) published an article dedicated to knives and cutting tools in diving. Its author, Kyle Kray, categorizes shark duels as fantasies and places entanglement in fishing line or abandoned equipment at the top of realistic risks.
The diving knife is therefore mainly used to get you out of a line trap. You still need to reach it with one hand, choose the right tool, and carry it without falling foul of the laws on bladed weapons.
We cover everything, from the placement on your vest to airport security checks.
What is a diving knife really for?
A diving knife is primarily used to free yourself when a line, fishing line, or piece of netting gets caught on your gear. DAN (2023) cites fishing line and abandoned equipment in frequented areas as the main risk for recreational divers. Everything else comes far behind.
The previous version of this page also listed signaling by blade reflection, defense against unexpected danger, or collecting shells. These uses have been removed. DAN reminds us that shark combat scenarios were fantasies from the early days of recreational diving, and no serious source considers the knife a defensive weapon against wildlife. A blade does not signal anything. To be spotted, a safety sausage or a well-chosen diving light does the job. As for shells, their collection depends on local rules, and elsewhere we explain why it is better not to touch marine life.
But the day a nylon line wraps around your tank valve, where your eyes see nothing, the cutting tool becomes the piece that allows you to finish the dive calmly.
An abandoned fishing net should be reported to the club, as our page on the diving net and waste collection reminds. Cutting it alone exposes you to entanglement.
Knife, line cutter, or shears: which to choose?
For fishing line and fine line, a compact line cutter is often sufficient and can be operated with one hand. A fixed blade knife or shears take over for thick rope or fabric. DAN (2023) notes that many recreational divers today are abandoning fixed blade knives in favor of line cutters, emergency shears, and knife-scissors, which are easier to store on the vest.
However, a small tool has its limits.
DAN reports the case of a diver wrapped in a wool blanket submerged in a river, against which a small line cutter was not enough. A hooked blade cuts monofilament. It struggles with braided rope or fabric. Hence the idea, expressed here as an editorial opinion, to combine a line cutter and a second sturdier tool, each in a different location. Regarding the tip, DAN explains that the blunt end now distinguishes diving knives from other knives because it limits injuries and damage to equipment. A sharp tip remains the domain of spearfishers.
As for maintenance, nothing complicated. Rinse the tool with fresh water after each dive day, dry it, then check that the blade still cuts and that the sheath holds the tool securely, as a worn attachment eventually fails when you kick against the current.
Where to wear your diving knife?
Wear your cutting tool where both your hands can reach it, even if one arm is trapped. DAN (2023) cites the vest pocket, the waist strap, the shoulder strap, the inflator hose, or the forearm. The belt is favored. Both hands access it the same way, and you can check at a glance that the tool has not fallen off during entry into the water.
However, the leg remains the location still shown in many catalog photos. DAN notes that these placements have caught on obstacles, retained dropped weight belts, and required too much movement to reach the tool. The detail of the weight matters. If you need to drop your belt in an emergency, a sheath on the calf can block it on the way. On the vest, this risk does not arise.
DAN also advises practicing grasping and using the tool with the same care as retrieving your regulator, and this is the kind of exercise that a training pool or a swimming pool allows you to do calmly.
Keep your tool within reach when you deploy your decompression buoy, as a line wrapping around your arm during deployment is one of the situations where it comes in handy.
What does French law say about carrying a diving knife?
In France, carrying and transporting a category D weapon outside the home is prohibited without a legitimate reason, according to service-public.fr (fact sheet verified on October 24, 2025). A fixed-blade diving knife can fall under this category. Going diving is the reason you will claim, whereas the desire to defend yourself does not constitute a legitimate reason in itself, the same fact sheet specifies.
The fact sheet classifies daggers, dagger-knives, and all objects that could constitute a dangerous weapon for public safety under category D. However, the legitimate reason is assessed on a case-by-case basis. Law enforcement, and then the judge in case of dispute, take into account the location, circumstances, and context. A knife stored in a diving bag on the way to a club on a Saturday morning does not tell the same story as a blade on a belt in the middle of the city. No receipt or certification card grants you immunity. They only help make your reason credible.
Carrying without a legitimate reason exposes you, according to the same fact sheet, to one year of imprisonment and a €15,000 fine.
In practice, keep it in its sheath at the bottom of your closed bag, and only attach it to your vest when gearing up. The previous version of this page presented utility knives as free to carry. The official fact sheet does not say that.
Can you take a diving knife on a plane?
Store it in checked luggage. The service-public.fr fact sheet on prohibited items in the cabin, verified on July 4, 2025, lists among them cutting, sharp, or pointed objects, including knives with blades longer than 6 cm. Measure your blade before closing your suitcase.
The fact sheet does not cover everything. Each airline publishes its own list, and the destination country applies its own laws on bladed weapons. Check both before departure. A line cutter or emergency shear does not necessarily pass better in the cabin, since the same fact sheet lists scissors among prohibited items. Put all your cutting tools in checked baggage. And think about the return trip, when your suitcase departs from an airport that applies its own controls.
For the rest of the equipment, our page on the diving bag and transporting your gear reviews baggage options, and a hard sheath around the blade prevents an agent or baggage handler from getting injured when opening your suitcase.
In short, a good cutting tool fits in a vest pocket. The wrong placement costs you the seconds when one hand is occupied and the other is groping around.
FAQ
Is a diving knife mandatory?
None of the official texts consulted for this page require it for recreational divers. DAN (2023) nevertheless classifies it among the safety tools to bring. Your club may also require it, so ask when booking.
Can you put a diving knife in carry-on luggage?
No, store it in checked luggage. The service-public.fr fact sheet (2025) prohibits knives with blades longer than 6 cm, as well as scissors, in the cabin. Also check the rules of your airline and the destination country.
What to do during a police check with a diving knife?
Calmly explain that you are going diving or returning from diving, with the knife stored in its sheath at the bottom of the bag. The legitimate reason is assessed case by case, depending on location, circumstances, and context (service-public.fr, 2025). A license or dive reservation can support your explanation, without automatic value.
Do you need both a line cutter and a knife?
DAN (2023) does not specify a number. A line cutter handles fishing line, a blade or shear handles rope and fabric. Carrying both in different places is an editorial opinion.
Where to attach your diving knife?
On the upper body, where both your hands can reach it: vest belt, pocket, shoulder strap, inflator hose, or forearm, according to DAN (2023). The calf has the disadvantage of snagging and hindering weight release.
Sources
- Can you carry a weapon for self-defense (knife, pepper spray, etc.)? (Service-public.fr, Directorate of Legal and Administrative Information, 2025)
- Dive Knives and Cutting Devices (Divers Alert Network, Alert Diver, 2023)
{“@context”:”https://schema.org”,”@type”:”FAQPage”,”mainEntity”:[{“@type”:”Question”,”name”:”Le couteau de plongée est-il obligatoire ?”,”acceptedAnswer”:{“@type”:”Answer”,”text”:”Aucun des textes officiels consultés pour cette page ne l’impose au plongeur loisir. Le DAN (2023) le range malgré tout parmi les outils de sécurité à emporter. Ton club peut aussi l’exiger, demande-le au moment de réserver.”}},{“@type”:”Question”,”name”:”Peut-on mettre un couteau de plongée en bagage cabine ?”,”acceptedAnswer”:{“@type”:”Answer”,”text”:”Non, range-le en soute. La fiche service-public.fr (2025) interdit en cabine les couteaux dont la lame dépasse 6 cm, ainsi que les ciseaux. Vérifie aussi les règles de ta compagnie et du pays d’arrivée.”}},{“@type”:”Question”,”name”:”Que faire lors d’un contrôle de police avec un couteau de plongée ?”,”acceptedAnswer”:{“@type”:”Answer”,”text”:”Explique calmement que tu vas plonger ou que tu en reviens, couteau rangé dans son étui au fond du sac. Le motif légitime s’apprécie au cas par cas, selon le lieu, les circonstances et le contexte (service-public.fr, 2025). Une licence ou une réservation de plongée peut appuyer tes explications, sans valeur automatique.”}},{“@type”:”Question”,”name”:”Faut-il un coupe-fil et un couteau ?”,”acceptedAnswer”:{“@type”:”Answer”,”text”:”Le DAN (2023) ne fixe pas de nombre. Un coupe-fil gère le fil de pêche, une lame ou une cisaille gère la corde et le tissu. Porter les deux à des endroits différents relève d’un avis de la rédaction.”}},{“@type”:”Question”,”name”:”Où fixer son couteau de plongée ?”,”acceptedAnswer”:{“@type”:”Answer”,”text”:”Sur le haut du corps, là où tes deux mains l’atteignent : ceinture du gilet, poche, sangle d’épaule, tuyau d’inflateur ou avant-bras, selon le DAN (2023). Le mollet a l’inconvénient d’accrocher et de gêner le largage du lest.”}}]}
