[maxerickson]

It's the density and incompressibility. When you slap water, it hurts because there is more incompressible water in the way of the water you slap, not because the film on the surface of the water is holding together. Falling into water from some great height is pretty similar to slapping it. A smoother entry dissipates the energy of the fall over a longer period of time, reducing the experienced forces (hence diving).

[peterwwillis]

Ah ok, not tension but area. So basically the less water you hit, the less force will be resisted.