* Hot spring: This is the most common and obvious answer. Hot springs are natural springs that produce water heated by geothermal activity.
* Geothermal power plant: These plants use hot water from underground to generate electricity.
* Heated pool: This is a man-made pool that is heated artificially.
* Warm water current: This is a naturally occurring current in the ocean that carries warmer water.
Could you please provide more context about what kind of warm water source you are looking for? This will help me give you a more accurate answer.
