Assuming you are doing the right thing, and optimizing your form for water entry, you will simultaneously be minimizing your wind resistance during the fall: 1.) A fall from 30 feet will result in a velocity of roughly 44 ft/s = 30 mph.2.) A fall from 100 feet will result in a velocity of roughly 80 ft/s = 54 mph..) A fall from 150 feet will result in a velocity of roughly 97 ft/s = 66 mph. 4.) A fall from 250 feet will result in a velocity of roughly 125 ft/s = 85 mph. The first case is a tower jump I did for the Navy, and is trival for anyone who is HWP and doesn't belly flop.
Fainting spells or feeling faint is caused by not enough oxygen getting to your brain. Passing out for a very brief period, coupled with a quick recovery, is medically termed syncope. And having a syncope moment will suddenly happen at some point in the lives of about a third of the population.
Cleveland_Clinic_Host: Syncope -- also called fainting, blacking out, or passing out -- is a sudden loss of consciousness, followed by a fall from a standing or sitting position. It is a condition that is caused by a decrease in blood flow to the brain. Blood contains oxygen, so when blood flow to the brain decreases, oxygen to the brain also decreases. Certain heart or brain conditions and a sudden change in position may cause syncope. Signs and symptoms include light-headedness, dizziness, cold sweaty skin, and feeling more tired than usual.