not by itself
Water waves are a form of mechanical energy, specifically a type of kinetic energy resulting from the movement of water particles.
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,.
The potential energy of the water in the tank.
Thermal energy
kinetic
That depends exactly what type of energy you are talking about.
Potential energy stored in water.
If you mean hydraulic energy, you don't really "convert water to energy". If the water is in a higher position, it has more energy (potential energy); when it falls down, this potential energy is converted to some other type of energy.
natural
potential and kinetic
potential and kinetic