Button operation under water
Is it safe to operate buttons of a G-Shock under water?
Casio itself is not sure about it ;-)

According to Casio Asia buttons or crown shall not be operated while watch is submersed in water or wet. On models labeled as “DIVER’S 200M” the buttons can be operated under water.

On the other hand G-Shock UK says: "Pressing the buttons on your G-SHOCK watch underwater is generally safe, as long as you do not exceed the watch’s maximum depth range."

Avoid detergents
Avoid wearing it in the bath or in area where detergents (soap, shampoo, etc.) are being used. Such conditions can reduce water resistance.

DIVER’S 200M
All Frogman models have a diving certification according to ISO 6425.