If this thing will only last 3 hours of battery as standalone using data, forget it! It should at least last 18 hours as standalone, or it's a waste of money.
The watch is water resistant but my advice, don't wash or drop the leather strap in water. That one is not water resistant. It can get wet. Or you can get the rubber strap. Wet leather makes the strap brittle. Degrade over time. So keep it dry.