The Casio G-Shock GA-2100-1A2ER watch is 79.64 euros instead of 99.75 euros on Cdiscount. It is waterproof up to 10 ATM, and can accompany you in the water and even during your shallow diving sessions.
The watch integrates a stopwatch at 1/100th of a second, and offers you three measurement modes, with elapsed time, intermediate time, and 1st and 2nd place times. It also offers you the possibility to program up to 5 daily alarms, and you can activate an hour signal.