Given,
Mass of the diver, m=70 kg
Height, h=5.0 m
The potential energy of the person when he was at a height of 5.0 m is

Where g is the acceleration due to gravity.
On substituting the known values,

According to the law of conservation of energy, his potential energy at the beginning will be converted to kinetic energy.
Therefore, the kinetic energy of the diver when he reaches the water is 3430 J