On a recent trip to DisneyWorld, we were lucky enough to get a day warm enough to swim in the pool.  My 6 year old is now swimming without a noodle, and my 4 year old still has a floatie.

But - they came up with a pool came they could play together in the shallow end - Leaf Patrol.

Each person in the patrol is trying to gather leaves from inside the pool.

They might be:
*At the bottom
*Floating on the surface
*On the ledge about to go in
*Near or far away

Collect them, and then take them over to the leaf spot to drop them off.  They used the pool filter.

They had fun for awhile with this, scavenging the area, collecting, and returning the leaves.  And they also felt a sense of accomplishment from making the pool better.