what is the potiential energy after hitting the water.?

Question

He jumps off a cliff 27m above the water and has a mass of 80kg.

Answer 1

The potential energy is the mass times g times the distance from the surface of the water to the center of the Earth.

Since the radius of the Earth is much, much greater than 27 meters, we model these types of dynamics in the incremental differences in energy and how it gets converted to other types of energy like kinetic and heat (from friction doing work).

So for this example, the difference in potential energy from the top of the cliff to the surface of the water is
80*9.81*27 J

Ignoring air friction, the kinetic energy when reaching the water is
.5*80*v^2

j

Answer 2

If the surface of the water is the datum then:
mgh=80*9.8*0=0