Swimming Pool Bowling
For swimming pool bowling, you need at least six people; two people in the shallow end and the rest in the other end of the pool. The people at the deeper end of the pool are the bowling pins. One of the two people at the shallow end acts as the bowling ball. The bowling ball person sits on a raft or inner tube and is pushed by the other person. The thrower starts pushing the bowling ball towards the pins and lets go after gaining some momentum. As the bowling ball starts towards the pins, the pins do a handstand under the water. Whoever gets hit as the ball comes down is a pin down.
Soaked Shirt Relay
Split up into two or more teams, depending on the number of people. Get a large T-shirt for each team. The first person jumps into the pool with the T-shirt on and swims from one side of the pool to the other. When she gets back to the other side, she has to take the wet T-shirt off and give it to the next team member. Repeat until all team members are done. For a more difficult version, add a diving mask and flippers that have to be exchanged along with the T-shirt.
Steal The Bottle
Steal the Bottle is similar to football. Split into two teams and have one team on each end of the pool. Place a chair at each end of the pool as the goals. Take the label off a 2-liter soda bottle and fill the bottle with pool water. Make sure the bottle top is on tightly. Have both teams turn their backs to the pool and have the referee throw the bottle into the pool and yell "go." The teams jump into the pool and try to grab the bottle and get it to the opposing team's chair. Each goal is worth a point and the first team to three points wins.
Rubber Duck Race
If there are a lot of people, split them up into groups of three or four. Then, have everyone line up at one end of the pool. Give each person a rubber ducky. The players' objective is to push their rubber ducks to the other end of the pool with their noses. No hands or other body parts can be used, including biting the duck. Players can try to knock the duck out of another player's way. The first person to get the duck to the other end wins. If there are multiple groups, have them each race, and then take the winner from each group and have them race again for the big winner.