Even if you don't have a pool in your backyard, a swimmingly good time is guaranteed when water's involved. So set up some sprinklers, blow up a baby pool or head to a community pool and get in the swim.
Set up lounge chairs and umbrellas near the "pool."
Place plastic balls, water noodles, rings and other water toys around the party area.
Cover the snack table with a blue paper tablecloth and decorate with fish stickers or, for older kids, scatter seashells and sand on top.
Buy paper plates, plastic tableware and napkins in an underwater theme. Stock up on paper umbrellas to decorate the kids' "cocktails" and create special "surprise" ice cubes by freezing a gummy fish in the center of the cubes, or, simply tint them blue using food coloring.
For indoor parties, string watery blue streamers and paper fish from the ceiling.
Let guests blow bubbles to create an underwater effect.
Have kids bob for apples in a baby pool.
Hold a race to see which child can collect the most floating toys (rubber ducks, rings) in one minute.
Find the flip-flop! Give each child one flip-flop and have them scour the yard or party room for its mate. Let them keep the shoes as a prize.
Do the limbo. Using a water noodle or rope, have kids limbo to a luau beat.
Fill water balloons and let the kids pelt the parents (swimsuit required, Mom).
For older, more experienced swimmers, award prizes for the best dive, the funniest jump and the biggest splash.
See who can collect the most water rings from the bottom of the pool in a single breath.
tip: for younger children, stick to the shallow end. Older kids and experienced swimmers can play this game in the deep end.
String up a net and play "beach" volleyball.
safety note: have other adults on hand to help keep an eye - at least one should know CPR. Get kids to show their skills by swimming a length or two in the shallow end at the beginning of the party, so you can determine who gets to swim in the deep end and who to watch closely. And keep a first-aid kit on hand just in case!