some knife considerations...
The blunt point is not for safety, but strength. One seems to do a LOT of prying with it. The blunt end works much better than any pointy kniife.

I prefer a double edged knife, one being serrated. Much of what you cut will be very fiberous. Old anchor lines, stringy matted vines that want to keep you down, things like that. The serrations make a big difference. The other edge, the normal smooth edge. for normal cutting.

Don't carry a shiny knife (or anything else shiny either) as many BIG fish will mistake it for a flashing small (food) fish. And their aim seems to be rather like a shotgun. They go after the flash and get your arm.

Strap it to your body. Not on your tank rig. You may entangle the tank rig and have to remove it. There goes your knife. I like it on my leg (inside left calf, I am left handed), but that is a personal choice. The thing is to make sure it can not catch the above mentioned vines or anchor rope. It can be like wearing a grapling hook on your leg if done wrong. And when it is afoul of weeds, you won't be able to un-sheath it to cut the weeds (catch 22?)

I did a lot of diving until a motorcycle accident (skull fracture) made diving impossible. Sure I had a few close calls diving, just as I have had close calls driving. But I sure miss diving. the best advice was given above. Do it by the numbers and pay attention to your instructors. It is not any more dangerous than many of the other things we do every day, but the environment is totally different and it takes awhile to become as knowledgable of the undersea world. Yep.. I sure miss it.