Danielle (Foodmomiac) keeps tub toys unmucky this way:
My four-year-old daughter has always loved the bath. She can easily spend upwards of an hour in the tub, so I'm always looking for ways to enhance the experience (both for her and for me!). One of my biggest peeves is dealing with storage of all of her tub toys. I used to use a plastic bin, but that doesn't breathe at all, and it always gets a gross film on the bottom from standing water. We tried one of those mesh duckie bags that attaches to the tile with suction cups, but it didn't work for us at all. The suction cups never held, and there was not even close to enough space for all of her toys.
The solution was found in the laundry department of my supermarket. This soft, foldable mesh bag allows all water to drain out, and lets her toys dry without gathering mold or mildew. The handles let me hang it on the tub faucet without having to fuss with finicky suction cups.
And a bonus hack!
My other tub tip/hack involves the toys themselves. Sure, my daughter has official tub toys, from musical dolphins to fish with a net, but her favorite tub toys are empty travel-sized shampoo and conditioner containers. She pretends the tub is a beauty salon and fills the bottles with water to "wash" the hair of the aforementioned dolphins, or the dozen naked Barbie Dolls floating around the tub.