If you drop your phone in water, dry it on a soft cloth or a kitchen towel. Next, put the phone in a resealing plastic bag with some uncooked rice, and leave it there at least overnight to dry out.
If a phone gets wet, take it out of the water as fast as possible to minimize any damage to the circuits. Turn the phone off. Remove the phone back, battery, SIM card, headphones and charging cable. Dry off as much water as possible using soft cloths, a kitchen towel or even a vacuum cleaner.
Fill a large resealing plastic bag with uncooked rice, silica gel or kitty litter. Place the phone in the bag, and cover it with the rice. Seal the bag, and leave it in a warm place for the rice to absorb the water. Depending on how wet the phone got, this can take several hours or even a couple of days. Once dry, reassemble the phone, and turn it on.
If the phone doesn't work, take it to an authorized repair shop for further help and advice.