I was told, some decades ago, that it was no longer acceptable to dive with a knife and one should just have one of those J-knife is it? thingies. 'You could damage coral' and 'Do you think you're going to fight a shark?' stuff.
Well, guess what? I still dive with a knife. The little J may cut fishing net but it sure ain't going to handle a rope.
I DO have the J in the car with the glass breaker on the other end - and a Leatherman too.
Remember: knives are no good unless they're sharp. Recollect seeing so many blunt Wilkies.