Related, I wonder how high the risk of drowning is in a situation like that. I expect I would impulsively gasp from the shock/pain and inhale a lot of water.
We had a nearby case where two special forces dudes drowned in parachute training exercise because due to wind changes they landed on a major river. Water landing is not safe even if you're an experienced skydiver, you may have to swim quite far to get to the shore while not really prepared for long-distance swimming, with all your clothing, boots, parachute and all that.