Individuals: Easy

• Choose one player to stand at the opposite end of the pool from the others and name a category, such as presidents or television program. The other players tell each other their answers--without the first player hearing. The first player starts naming things from that category. If he says one that matches another player's answer, both players must start swimming to the opposite ends of the pool. Whoever wins gets to name the next category.
  
  

Individuals: Hard

• Host a pool Olympics that include an obstacle course, a distance swim and an underwater competition. For the obstacle course, time competitors as each takes a turn swimming through large hoops, pushing a ball through the water, grabbing a penny off the pool and the like. For the distance swim, have each competitor dive in and swim back and forth across the pool as many times as he can without pausing. For the underwater competition, do the same, only this time players must hold their breath and swim underwater.
  
  

Teams

• Set up a soccer game across the width of the pool--make it lengthwise if everyone is a good swimmer. Set up goals on both ends, such as a float with a bucket on it or an inner tube. Divide the teams and have them follow these simple rules: The player with the soccer ball must either shoot or pass, not move. Everyone else can move. The ball is passed around until either a team shoots and misses, shoots and scores or the opposing team intercepts it. When a goal is scored, the defensive team becomes the offensive team and vice versa.
  
  

Couples

• Hold a race back and forth that stresses togetherness by having couples hold onto each other throughout the race. In the first lap, one of them can use only his legs, while on the return he can use only his arms. The reverse is true for his partner. Any couple that breaks apart while swimming or violates the rules is disqualified.
  
  

Anything Goes

• A free-for-all game that is more silly than competitive is great for a big group of swimmers. Divide the pool in half with a rope and put an equal number of toys or other floating objects in each half. There should be a lot. On your mark, players from each side pick up the objects and toss them to the other side, as fast as they can--including the ones being thrown by the opposing team. When you yell "Stop," count the items on each side. The winning team is the one with the fewest toys.