Dive knives and line cutters: which do you need?

Why it matters here

We run into fishing line and nets more than you’d think. Most people who get their line caught just abandon it, and those of us who scuba dive are usually the ones picking it up afterward.

It’s not just cleanup. A few years ago, one of us got hooked by a fishing line, dive flag up and all, and a dive knife cut it before it turned into a rapid ascent. Another time, we were picking up a line that was just lying on the bottom when someone at the other end started tugging, and it almost took a finger. Thanks to the knife, we just cut the line.

Three kinds

• Line cutter: a small hooked blade that slices monofilament and thin line. Light, cheap and easy to mount. Every diver should carry one.
• Dive knife: a larger blade with a smooth and a serrated edge for rope and heavier line.
• Shears: cut through line and thin cable that a knife struggles with.

Which one is personal preference, and depends on how well you handle cutting tools. Ours is a solid knife.

Tip and material

• Blunt tip: safer on your gear and yourself. What most scuba divers want.
• Pointed (dagger) tip: what spearfishers need, to put a fish out of its misery quickly when the shot didn’t do it.
• Titanium: doesn’t rust, even in salt water. Stays sharp a little less.
• Stainless steel: holds an edge well, but needs a fresh-water rinse after every dive.

Titanium and stainless are both solid. It comes down to how much you want to spend.

Where to carry it

• Wear it where it’s easy to reach: your BCD chest strap, waist or a hose, somewhere either hand can get to it.
• Many divers carry two, one on each side, in case one hand is caught.
• If you use a leg knife, make sure you can actually reach it, and wear it on the inside of your leg, not the outside, where it’s more likely to snag line.

Care and what not to do

Rinse every knife properly with fresh water after a dive, dry it and check the sheath clip still holds. Don’t use it as a pry bar, a pointer or a tank banger.

Flying with a dive knife

It has to go in your checked bag, never your carry-on. And check the rules at your destination: even though a dive knife is a tool for divers, some countries consider it a weapon.