You can try putting your watch in a small air tight bag with a cup of long grain rice (raw rice grains) and leave it in the bag and seal it.
Keep the sealed bag containing the watch and rice, in a warm place.
Gently lift the camera module so that it is facing forward - this helps any moisture evaporate and be absorbed by the rice.
This can take a few days, and it definitely helps if it is in a warm (not hot) place.
If it got wet, it is surprising that the watch remains powered on…
So there is a chance that it is not moisture inside.
Usually you will see condensation in the camera lens - if there is moisture inside.
Another possibility is that the screen connection to the motherboard has been interrupted.
Usually this happens if the watch has been dropped or knocked.