h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Not an errata, more a matter of opinion, but I would never mount a knife on my legs. If it's on the front, you increase your snag potential, and if your legs brush together while swimming, you are putting strain on the strap/buckles of the knife. depending on how it is attached, you may make it more likely become loose and then not there when you really need it!

Also, it is further down to reach when you really need it, when you might well be a bit panicked, and thus more difficult to see. If you have it on a nylon lanyard so as not to lose it if you drop it, a lanyard from your leg gives you less reach than one mounted higher up, a longer lanyard to give you the reach you would like gives you more snag potential with more lanyard floating about!

Far better, IMHO, to mount the knife on the chest, maybe on one of the chest straps. More easily reachable with either hand, easy to see and replace. No more snag potential than the front of your BCD/Harness has anyway and not under strain when you swim.

Dive safe and live long...

I always dove with my knife on the inside of my leg, and I never had any problem with brushing it with the other leg. I swim with my legs a bit apart more to keep the fins from fouling each other than worries about the knife.

The model I used was a US Divers knife that came with a hard plastic sheath that locked the knife into place. You had to push a button on the front and give it a tug to get it free. It stayed with me through some extremely rough beach entries and exits.

I was never very comfortable of the idea of having a knife mounted near vital organs AND vital dive equipment. If my knife comes loose from my leg, it's just going to fall to the bottom, perhaps giving me a cut on the leg or fin along the way. If my knife comes loose from my chest, it could cut a hose, pierce the BC, or a whole lot of even more important things if the surf picks up.

All the guys who carried one on their chest carried these wee things. You can put a big knife on your leg.

Perhaps I should have qualified my opinion further -

Firstly, my knife is quite small, it's only real use it to cut monofilament line, which is all I want it for, and secondly it has a squared off tip so I'm in no danger from it, nor is any inflatable boat I get into. Personally I see no need for me to have a big knife, a small one will do what I want, and creates less problems than a bigger one.

Each to their own!

I view my knife as a sort of all-purpose tool, and the more things it can do, the more useful it'll be. I always figured the worst-case scenario is getting tangled up in some netting or kelp, if I dove a kelp bed, so I'd want to be able to hack through that stuff pretty easily. I might also want to pry loose a mollusk stuck in some rock, use it as a reflective tool to signal my partner if we get separated, pound the hilt into an overly-curious shark (definitely wouldn't want to use the other end, it might make his friends think it was me bleeding), cut loose some snagged equipment in an emergency, etc. The idea is you never know what you might need it for, but you're ready for it when it happens.