potential and kinetic
potential energy
Mechanical energy, if it is moving then it is kinetic mechanical energy. Or if it is at the top of a hill about to fall then it is potential mechanical energy.
Gravitational potential energy is converted to kinetic energy of the fall. Some of that is then converted to heat which helps water to evaporate and to slightly increase the water temperature at the foot of the fall, some is converted to the noise of the waterfall, some is used to erode rocks at the foot of the fall.
Kinetic energy
Water waves are a form of mechanical energy, specifically a type of kinetic energy resulting from the movement of water particles.
gravity
Stored energy
The type of energy which is used to boil water is commonly heat energy. This will result to a changes from the liquid state to gaseous in form of water vapor,.
kinetic energy because kinetic energy means moving
not by itself
potential because it hasn't fallen yet so its not using any energy
The same as any other falling object. When it is at the top, it has gravitational potential energy; as it falls, that's converted to kinetic energy.