Cosmos is the best dog park I've been to in Gilbert! They have many different sections for big and small dogs. The water part is the best part of Cosmo, although the water is a little bit muddy and there is stagnant mossy water where the dogs don't swim my dog loves it! I will suggest the you bring shampoo to wash your dog after they swim in it because it does make your dog smell a little bit. They make it convenient for you though because they have three different hose stations where you can wash your dog off!
I will also suggest that you do watch your dog closely because there are a couple of different dogs that I've encountered that are very protective over their tennis ball and will get very aggressive towards other dogs, but that is going to happen at any dog park!
I definitely suggest to bring your dog here, you and your pup will have a blast!