Once upon a time, I was working as a commercial diver on a job in Newark Bay, in New Jersey. The company I was working for was an established heavy construction company, but this was their first marine construction project. We were installing a gas pipeline from one side of Newark Bay, to the other, it was winter, and I was the first commercial diver the company had ever hired.
Because of pollution concerns around digging into the Newark seabed, they were using directional drilling technology from the oil fields as opposed to just digging a hole and plopping the pipe in it. They were going to drill a hole from one side to the other, and pull the pipeline through it across the bay. Anyway, I had made my first dive for this outfit, and was standing around on deck in my drysuit because the dockbuilders were moving the barges around. One of the barges was being relocated, and the tugs were just getting it underway.
As could be expected with a company new to marine construction, someone was not on the same page as everyone else. One of the drillers had tied a 2" hawser line from an equipment trailer on the departing barge directly to the stabilizer of the crane on the spud barge. As the departing barge was cut free, the line to the crane was missed because there was so much slack it was laying in the water between the barges. As the departing barge is moving off, the offending line starts to tighten, and it is first noticed by the Project Super. He starts yelling, guys are pointing, people are running around, and the now tightening line cannot be untied from the crane stabilizer, and the tug cannot stop the departing barge.
The Dockbuilder Foreman is standing right next to the line, the Super is still yelling, the line is getting really tight, radios are crackling, and the situation is really not good. Something is going to give, either the line, the trailer on the departing barge, or (hopefully not) the crane? The directive is, "Cut the line!! Cut the freaking line!!!", which of course is the correct answer. However, after a pocket check, the next words out of the Foreman's mouth are, "Someone give me a knife??" Now practically all commercial divers and most dockbuilders carry folding knives, but it appeared that no one had an available knife, folding or otherwise, to cut the 2" hawser.
I never liked folding knives for hardhat diving. Everyone from dive school on down had folding knives, even guys I really respected as divers. I often carry a folding pocket knife, but for diving I like big knives, also known affectionately as BFK's, for Big Freaking Knives. BFK's are tools suitable for all sorts of hammering, prying, chiseling, measuring, and cutting stuff that commercial divers, and wreck divers, may need to do. Aside from that, when attached to my thigh, I am able to deploy it quickly and easily, even with cold hands, without the fumbling around necessary to open a folding blade in the water. BFK's have always made sense to me, besides they are sexy.
Back on the barge as the end of the world is nearing, everyone has their palms to God while I sprint the 10 yards to the crane stabilizer, while pulling my BFK out from the sheath on my thigh. Sliding like I was coming into second base, I place my knife blade to the tensioned 2" hawser line… and it cuts it like a hot knife through butter in two strokes; in about half a second. It was beautiful.
The disaster was averted, and of course the Super wants to know who I am? In 20 years of commercial diving, I never made more money on a job than I did on that one. The Super loved to keep me around. It was all because I had a sharp knife within reach when I needed it.
I still dive with a BFK on my thigh, within reach, and yes, I get lots of kidding about it. References to rogue sharks, Crocodile Dundee, sword fights and all sorts of other good natured teasing are routine with people who do not know, or understand me. If you dive without gloves, and don't touch anything, then you don't need much of a cutting device. However, that is not me. IMHO, wreck diving is a contact sport by its very nature.
Diving the way I do, I prefer a BFK on my thigh for a bunch of reasons. First of all, access is imperative. If you cannot easily access and stow your knife, then you are less inclined to use it. The relationship is directly proportional. Wrecks are full of monofilament fishing lines, trap lines, nets, cables, and all sorts of other potential entanglements. I am inclined to cut anything that poses an entanglement threat, because I keep my knife sharp, and I can deploy and stow it easily, without even looking. I not only regularly cut entanglements, but I do it quickly and easily, usually on the fly. You are welcome.
Now, some divers carry neat little cutty devices in cute little holsters that may save their lives in an entanglement emergency, but are they easy to use and to stow? Nice for caves, not for wrecks. There are other divers whose knives are stored away like the crap they keep in their basement, just for emergency!! By the way, an emergency is probably not the best time to use something that you never use otherwise.
On more than one occasion, I have gotten a little bit lost out in the sand between wrecks or reefs. On other occasions, I knew where I was but I had to search for something that was lost on a featureless seabed. With my BFK, I can stick it into the sand, tie off my reel, and do a little search pattern. I have also had a problem with sticky shackle pins, or other equipment, that needs a little hammering to make it work right. The anchor chain can sometimes cut into the wreck and on occasion it needs some persuasion to come out so you can go home. I can't do any of that with a little blade suitable for cutting my toenails.
The catalogs used to call the BFK a Diver's Tool, because it is so much more than a knife. It can do any number of tasks in the hand of a capable diver. At the same time, I keep it accessible, I keep it sharp, and I keep it busy. The trend is for smaller, lighter, friendlier looking "cutting tools", which is very politically correct, but not necessarily as utilitarian as I prefer. It is not easy to even buy a brand new BFK these days, so I guess I better try not to lose this one???
Honestly, we all know size is not everything, and a BFK is not for everyone. Add to that, what is big to one diver is not necessarily big to another diver? Maybe you have short thighs, or maybe you don't take teasing well? Regardless, whatever you are carrying for a cutting tool, it needs to be sharp, you need to be familiar with it. Wherever you carry it, it needs to be ready for when you really need it. Feel free to translate this concept into your real life, not just for diving.