They will rent you a tube for usage at SAB (not sure if it's hourly or daily as I've never done it). If you bring your own tube, they can stop you from using it as they have certain rules to follow. Some people have been allowed to use their own clear tubes, while others have been told no. There are only a certain amount available for rent. However, you can certainly buy your own noodle and use that which is much cheaper. We always pick up a couple of noodles from publix when we arrive ($4.00 ec) and use them during our trip. On the last day, we give them away. I don't know if they sell noodles at the resorts.