Using this G - Shock watch is a breeze. To access the world time and stopwatch features, just use the buttons on the side of the watch. Press the large front button to turn on the high - brightness LED light when you're in the dark. When it comes to water resistance, it can handle up to 200 meters, so you can wear it while swimming or snorkeling, but don't try deep - sea diving with it. For maintenance, keep it away from extreme temperatures and strong magnetic fields. Although the battery lasts about 10 years, if you notice the watch is running slow or the display is dim, it's time to replace the CR2025 battery. You can take it to a professional watch repair shop for battery replacement to avoid any damage to the watch.