One day the watch fell in the water and then it is not working

"That's a start. Getting rid of the water is the right move, but I would add disconnect the battery if you can get the device open. Omit the rice and dry it up with a paper towel as best you can, leave it to dry.

However. If damage was already done to circuitry, drying it out will not undo the existing damage. It does prevent further damage. And maybe you'll get lucky and it will turn on. But in my experience this isn't the case."