Did the parachute not simply open before he landed in the water? He can't remember that part, and he only woke up after the parachute was under water and yanking on him. Either way, refreshing to see a well written piece.
The closed parachute acted as a streamer, slowing him down enough to cause only severe injury on a water landing. Had the parachute opened, an unconscious water landing would not have caused such injuries. That would only happen at speed. Am a licensed skydiver.
I don’t know how fast he was falling, but even in water it seems almost impossible