The thing is, if you are in the water, flapping your arms and kicking legs as hard as you can usually keeps you afloat. The same can't be said for when you are falling through the air...
One thing that CAN be said about both falling though air and struggling in water is that if you do flap your arms and legs around you will almost certainly make things worse, probably MUCH worse.
In the case of falling through air you will be MUCH better off to "arch" (verb) making yourself kinda/sorta flat which will keep you speed down as well as keeping your back up.
So that if/when the automatic reserve deploys you are in the best position for it.
Don't "go fetal" that will roll you onto your back and could result is some serious opening shock, bad position and higher speed.
Calm, Ya gotta stay CALM.
Most difficult situations that develop into disasters do so because people (temporarily) forget their emergency training, most important of which is "Don't panic" (yet) (-:
This is opinion - but I don't believe emergency drills are practiced enough in most scuba diving - classes or recreational dives. The culture seems to be you need a dive buddy and if you have one you're covered.
Well, only if your buddy is within ONE breath's reach )-;
Oh Yeah, I believe in helmet wearing for sky diving.
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I think the "work" focus of operating tractors and implements (mentally) masks the risks, whereas in "adrenalin rush sports" we are very much aware of our exposure and (hopefully) are consciously preparing ourselves for the things that could go wrong.
Risk management 101 ? Yeah, probably.