The thing about a dive knife is that you never need one until you need one real bad.
If you become entangled in fishing line (often very hard to see if it has not been in the water long), a gill net or even your own dive line, a knife is an essential tool. The first death of a diver I personally knew involved a diver who drowned about a foot under the surface on a drift dive in low viz after getting entangled in his dive line and a submerged tree. To make it worse, he had a knife mounted on his calf where he could not reach it when he needed it.
Some lines, scuh as spider wire and steel leaders are very hard to cut with a knife so a pair of EMT shears is good to have along.
In springs, caves and quarries, I usually have a z-knife for lines and a small dive knife, both mounted where I can reach them with either hand. (In many quarries a dive knife is not allowed due to ignorant and thoughtless divers carving names in stuff, drying open mussels, etc, but they will often allow a Z-knife or EMT shears.) Off shore or in larger heavily fished lakes where tougher to cut leaders may be encountered, I add the EMT shears carrying them in a pocket.
Very well put. Most of my dives are in areas of high entanglement risk because they are heavily fished and dived, and they are around wrecks or artificial reefs. About six weeks ago, I had to share air at 78 ft. in open ocean with a diver who became entangled in a reel line while ascending and ran out of air while trying to remove his BCD and untangle the line from his tank valve. A week later, another buddy got "mildly" entangled in his own reel line while ascending in open ocean, so instead of trying to untangle it before it got bad, he learned from the lesson of the prior week and just cut his own line.
I can also name at least one incident where a diver had to leave his gear behind and surface from 50 ft. when he became entangled in fishing line while diving around a heavily fished wreck. I have read of one incident where a diver drowned trying to free herself from a fishing net during a commercial-type dive, but dropped her knife and couldn't reach it. Other entanglements come to mind where divers drowned after becoming entangled.
I have personally been "mildly" snared a couple of times by fishing line around wrecks, and came close to a reel line entanglement about a month ago, but ducked, grabbed the line, turned and faced it, then slowly worked myself away from it before it snagged my tank valve. I believe I would have been snagged several more times over the years if I had not been watching very closely and moving very slowly, which is what you should do, especially around wrecks and high entanglement risk areas. I have also used a knife to cut line when I used to spearfish years ago and got lines tangled up, and have seen several dive buddies use knives for the same purpose. One diver even went as far as using his knife the entire dive, poking around in the sand exploring so he wouldn't expose his fingers to the unknown (I don't agree with this use of a knife!).
Some certification agencies require at least one cutting tool for Rescue Diver level training or above, but I have always carried one. Now that I have named at least eight (8) specific incidents/reasons, you can understand why I
always carry
three cutting tools....one fixed blade titanium primary knife, one folding blade titanium backup knife, and EMT shears. I position each one where I can quickly grab them with either hand and just hope to heck I never have to use them again.
The key is to stop, think, act, and move slowly so a mild entanglement doesn't become a major one, but have a cutting tool just in case you need it.
Hope this helps!
