For starters, find out whether or not your hotel has a dress code. It's highly likely you'll be provided with a toweling robe and slippers, but not necessarily. Underneath, make sure you're as comfy as possible; yoga bottoms, track pants, sweatshirts and T-shirts are often suggested attire. Sports shoes and trainers are usually allowed, but limited to dry areas. It's also a great idea to bring a second swimsuit or an extra set of clothes along with you.