Besides diving, what's the next best way to jump into (deep) water from an average height?

The best way is feet first, toes pointed down, your hands tight against your sides (fingers pointing down). Spread your arms and legs the instant you feel water on your face, so you stay as close to the surface as possible.

Diving isn't the best way. Diving from enough height could break your neck. (Water is about as soft as concrete if you're diving from enough height.)

Feet First the First Time - this is the best way to jump into any water that you are not absolutely familiar with. So if there was an emergency, the best way would be feet first. You would be less likely to endanger yourself.

This is because if you cannonball, or dive, you are likely to injure your spine or back, if there is some obstruction you are not familiar with.

Also, you should have your knees slightly bent, not fully bent, and not locked straight, as you are more likely to cushion yourself.

Funnily adequate you may get injured from that top into water, the clarification why we don't get injured is by using the fact water strikes so the exterior of it breaks up in basic terms like working right into a wave. in case you look into the Olympic diving of the boards and stuff they bubble machines in the water to interrupt the water up otherwise those men could smash the bones leaping from those heights

Jumping. A cannonball creates a centered heavier landing causing you to sink further down faster.

Well, rescue divers drop in feet first, but you should be bold and daring.... go for the cannon ball!

feet first