Whitewater Creek Park is off of the Palisades Unit of the Chattahoochee River. While the park is open for swimming (for people), many bring their dogs. As long as the dogs are on leash, they can romp in the water, too.
Once you park (be sure to pay the $3.00 park fee), the walk is just a few yards away. The beach is long and sandy and the river is shallow to about the middle of the river. Wear water shoes as there are loads of rocks and boulders in the water that are easy to slip on. Many people make their way to the outcrops of rocks scattered in the river to sunbathe and watch the rafters, kayakers and canoes go by.