First of all, find out if your hotel has any sort of dress code. You'll probably be provided with a robe and slippers, but not necessarily. Underneath, you should plan to be as comfortable as possible; track pants, yoga bottoms, loose-fitting sweatshirts and T-shirts are often recommended. Trainers and sports shoes are usually permitted, but confined to dry areas. It's also a good idea to bring a second bathing suit or some extra clothing along with you.