The most frequent cause of water blisters is repeated friction.
The best course of action against blisters is to try to prevent them in the first place. Blisters are most likely to occur during unaccustomed activity or with new equipment. Try to use gloves when working with your hands in activities such as wood working or gardening. When hiking, use well worn-in shoes or boots and change socks frequently. Socks wet from sweat are more likely to cause blisters than dry socks.
Once you have blisters, try to treat them as soon as possible. If you will continue to perform the activity that caused the blister, cover the blister with a bandage or other protective covering, such as moleskin. If the blister breaks, it is more likely to become infected, so it is best to keep the blister covered. Try and take a break from the activity to give the blister time to heal.
If the blister seems likely to break, it is better to drain it yourself rather than have it tear open. Wash the area gently with soap and hot water, being careful not to tear the blister. With a sterile needle, make a small puncture in the side of the blister close to the undamaged skin. Gently drain the fluid, then cover the blister with a sterile bandage.
Over-the-counter pain relievers such as aspirin, naproxen, and ibuprofen will help ease the pain of blisters and reduce swelling. An ice pack or cold compress applied to the blister will also reduce swelling and discomfort. Keep the blister clean and dry and give it time to heal before engaging in activities that might cause it to break. As with all injuries, if home remedies do not seem to help or if infection occurs, see your doctor for treatment.