Cool gif!

Okay, so what did you learn?

• Take half a breath (not a big gulp of air) because a pressurized torso is going to take more impact damage than a somewhat compressible one.
• Cross your feet and arms and pull down on your life vest with both hands, and always enter the water feet first. You might break your legs, but it's better than breaking your neck, and you're less likely to get "wishboned" -- that is, torn apart when your legs go in two separate directions on impact. (You still might, though.)
• Speaking of breaking your neck, that's exactly what you'll do if you forget to hang on to your life vest. It will strongly resist being pulled under water, resulting in something like videos where someone dives into a pool while holding a ball, causing the ball to shoot twenty or thirty feet into the air -- only that will be your head, not a ball. It may stay attached, but not usefully so.

Almost better not to wear the lifejacket and get one afterwards. 

But what if you're unconscious?

Good point Geege. 

I wish I could get the phrase "wishboned" out of my head.