the diving knife

\A diving knife is a simple, reliable tool that can quickly get you out of dangerous or annoying underwater situations — especially entanglement — and it’s useful for routine tasks.

Why carrying a diving knife is a good idea

• Cut entanglements fast — fishing line, monofilament, netting, kelp or abandoned lines can trap you or your gear. A knife lets you free yourself or a buddy quickly.

• Rescue tool for others — you can cut a trapped buddy free or free their gear. That can make the difference in an emergency.

• Tool for gear problems — cut away snagged straps, trim damaged equipment, or remove stuck lift-bag lines.

• Signal & prying (limited) — you can tap or point to attract attention; some use it to pry loose things — but prying should be avoided with small knives.

• General utility — small underwater jobs: cutting tape, opening packaging on a boat, trimming rope.

Typical knife features & what to choose

• Size: recreational divers usually use 2.5–6 inch (6–15 cm) blades. Shorter is easier to carry and safer; longer is heavier and more like a tool for specialty dives.

• Blade type: partially serrated (for line) + straight edge (for clean cuts) is common.

• Material: corrosion-resistant stainless steel or titanium; stainless is cheaper, titanium resists corrosion best.

• Sheath & mount: secure, low-profile sheath that locks the knife in place. Popular mounting locations: lower leg, calf, or BCD/wing pocket. Choose what’s accessible but won’t snag.

Placement & accessibility

• Accessible: mount so you can reach it with minimal finning and without removing other gear.

• Secure: use a sheath with a positive lock. A loose knife is a hazard.

• Practice reaching for it in calm conditions before you need it.

Safer alternatives / complements

• Line cutters / shears: faster and safer for cutting monofilament; a good complement to (or replacement for) a knife for many divers.

• Dive scissors: small, effective for line and tape.

Maintenance

• Rinse with fresh water after every dive, dry, and apply light oil occasionally.

• Inspect locking mechanism and sheath regularly.

Safety & legal notes

• Don’t use as a weapon. A knife is a tool for safety and utility, not aggression.

• Check local rules. Some operators or locations have rules about carrying knives — always respect them.

• Get training. Learn safe carry, retrieval, and use techniques (practice in controlled conditions).

Quick rule of thumb

If you dive in areas with fishing gear, kelp, wrecks, or do technical/boat diving, carry a cutting tool (knife or dedicated cutter). In clear, shallow, low-risk shore dives it’s less critical — but many divers still carry a small tool “just in case.”