First of all, check if your hotel has a policy in regards to dress code. You'll probably be provided with slippers and a robe, but this isn't always the case. Underneath, aim to be as comfy as possible; tracksuit pants, yoga bottoms, sweatshirts and T-shirts are often recommended attire. Sports shoes and trainers are normally permitted, but restricted to dry areas only. It's also a good idea to bring another swimming suit and an extra set of clothes with you.