If a ceiling fan is going to be mounted instead of a light fixture, a would need to be installed.
Easiest to wire is a single light that occurs at the end of a circuit.
The two conductor cable from the ceiling box to the light switch is supposed to have the white conductor re-identified with another color because it is not being used as a neutral, but as a hot wire.
Legrand Pass Amp Seymour Rcd33wcc6 White Single Pole 3 Way.
This way, when you flip the light switch off, the water will also turn off.
Turn the power off again.