Spearfishing - Cutting Devices

How to choose a dive knife for your discipline 

Discipline drives the knife choice more than personal preference does. 

Spearfishing knives need a sharper point for dispatching fish humanely, a blade length around 8cm to 12cm, and a secure sheath that does not lose the knife mid-dive. Bicep and forearm mounts keep the knife clear of your float line and the speargun rigging. 

Scuba safety knives often have a blunt or rounded tip to avoid puncturing your BCD, your wetsuit, or yourself in an entanglement scramble. Single-hand release sheaths matter; an entanglement is the wrong time to be fiddling with a two-handed clip. 

Line cutters are the simplest safety tool. Small, fast, mounted on the BCD inflator or weight belt, designed for a single quick cut on monofilament or net. Most divers carry one regardless of whether they also carry a knife. Freedivers typically carry a line cutter rather than a knife. 

Material affects how long the knife lasts. Stainless 316 is the common standard, holds an edge well, and is fine for regular rinsing after dives. Titanium is more expensive but resists corrosion better, holds up over years of salt-water use, and is lighter. For an occasional diver, stainless is the better-value buy. 

A note on carriage: a dive knife on a beach is legal where it is in use for diving, but should be sheathed at all times outside the water. This is general guidance, not legal advice. For matching a knife into a wider kit, see the spearguns collection and the spearfishing rigging collection for line and shaft replacements.