Remember on my birthday how after lunch I had to go back to work while the boys stayed downtown? They went to the National Building Museum for a special event: The Beach. They created this giant ball pit with clear balls and called it the beach. I'm sure you can guess that all three of my boys had a great time. Good thing, because this beach ain't cheap.
Tip: If you go, do NOT wear white. Put your kids in bright colors so they're easily spotted should they start drowning.