I am glad I researched the subject, and made my decision based on reality, not hype.
This is what beginners think they want, and most diving shops are happy to offer them all sorts of knives. Sometimes, for a very steep price. 150-200 bucks.
What scuba divers really need is a cutting tool to get out of entaglements. You’ll be surprised to learn how many fishing lines, nets, etc. are lurking down there. You need a tool, not a weapon, and a backup tool: Reliable, easy to use and disposable, like these.
This Spyderco knife is made in Japan from unique precipitation hardened H1 steel that doesn’t corrode in ocean water. I was surprised to find it on sale in Walmart. It’s razor sharp, and it’s a favorite among veteran divers.
At $3.65, tax free and free shipping these sheers are very disposable, and I bought a few of them.