It's a lucky kid who's born in the summer with years of wonderful outdoor celebrations ahead. This birthday, make the most of the backyard's resilience to good messy fun with a water theme that allows children to splish and splash and parents not to worry about untidy results.

To create a watery world, you don't need an adult-size swimming pool -- just lots of blue and green decorations, a menu inspired by critters from the sea, and a few aquatic activities.

What makes such a simple party memorable for the guests? There's a single theme that's expressed creatively in all the details. Start by setting the tone weeks before with invitations that hint at what's to come. Look for store-bought cards, or create your own -- a project you and your birthday boy or girl can work on together.