Solution:

To find the odd one out among the given options, we need to analyze the characteristics and properties of each option.

Solar:
- Solar energy is obtained from the sun.
- It is a renewable source of energy.
- Solar panels are used to convert sunlight into electricity.
- Solar energy is clean and does not produce any harmful emissions.

Thermal:
- Thermal energy refers to the energy that is generated from heat.
- It can be obtained from various sources such as burning fossil fuels, geothermal energy, and even solar energy.
- Thermal energy is often used for heating purposes, such as heating water or buildings.
- It can also be converted into mechanical energy to generate electricity.

Water:
- Water is not a form of energy, but it can be used to generate energy.
- Hydroelectric power plants use the force of flowing or falling water to generate electricity.
- Water is a renewable resource and does not produce any emissions.
- It is widely used as a source of energy in many parts of the world.

Nuclear:
- Nuclear energy is obtained from the nucleus of an atom.
- It is a non-renewable source of energy.
- Nuclear power plants use nuclear fission to release energy from the nucleus of atoms.
- It is a highly efficient source of energy but also comes with potential risks and concerns.

Analysis:
Among the given options, the odd one out is water because it is not a form of energy itself but rather a resource that can be used to generate energy. The other options, solar, thermal, and nuclear, all directly represent different forms of energy.

Conclusion:
Water is the odd one out among the given options as it does not directly represent a form of energy.