Just wanted to add that there are a few situations an OW or AOW diver could find themselves in, where bad technique could possibly lead to an accident:
A tropical vacation swim-thru (like those coral ones in Belize at 50ft). One of the group silting out the other divers behind them could lead to disorientation, snagging of gear ... possibly panic & all in a partial overhead environment.
A hollowed-out wreck swim-thru (essentially a novice dive) - same scenario.
At this point, I'm not even sure what I'm ranting about! :P Except that it has to do with people who should know how to fin but don't or don't care to! & all the subsequent problems it causes for anyone else. & then all that crankiness about when they should've learnt it and wondering if there's a nice way to hammer it into their heads at this late point in time....
Geez, I am cranky!
I think I will go attack the crunchy snacks now.