Funny how people can’t accept simple physics. Golden Gate jumpers even know this - water has the same density as concrete at high speed. Considering terminal velocity is not even reached on that jump, it does not have to be even much greater than 100 mph to do real damage.
I saw those responses and decided it wasn't worth it to engage them. That they don't understand the difference between a belly flop where a human being goes belly first into the water from a few feet high, vs. a large aircraft hitting water while at high speeds from thousands of feet above pretty much tells you everything you need to know about their logic and reasoning skills.