>>257993Seconded.
As a freediver myself, I got tangled plenty times in lines and nets left astray at the bottom of the sea, not to mention, fucking pic related.
It's very hard to keep your calm in such a situation, and even harder to get out without a knife. I actually have two, one on each forearm which I can easily take out with either hand, just in case one of my arms gets stuck or something. It saved me a couple times already.
I find it stupid to go on a dive without one actually.