Firstly, check whether or not your hotel requires you to stick to a dress code. It's likely you'll be supplied with slippers and a robe, but this isn't always so. Underneath, aim to be as comfortable as possible; tracksuit pants, yoga bottoms, loose-fitting T-shirts and sweatshirts are often suggested attire. Sports shoes and trainers are usually allowed, but limited to dry areas only. It's also smart to bring a second bathing suit or a change of clothes with you.