Button operation under water
Is it safe to operate buttons of a G-Shock under water? => Only on Frogmans!

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.

G-Shock UK says basically the same: "We generally advise to not press the G-SHOCK buttons underwater. [...] Our ISO divers certified G-SHOCK's such as our FROGMAN range can be operated underwater [...]"

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.