I ordered the 4t-5t one because my son is just barely starting to fit 4t clothes and I wanted another summer out of it hopefully.  It fits him well and is slightly lose as I was hoping. To my great surprise and joy, the hat actually fit his large head! Normally I have to buy him adult women's hat since his head is so big; so I was very happy.

We haven't tried it in the water yet or washed it, but I'll update this after we do.

So far the only problem is that he looks like a beekeeper. XD