You face little risk breaking a tooth while swimming – barring a bump to your mouth against a hard wall – but you still want to protect your mouth over long periods of pool time. One of the best ways to do this if you're an avid swimmer is to make sure the pool you swim in is well maintained. If the pH of your swimming pool is too low (meaning it's too acidic), according to Delta Dental, you're at a higher risk for "swimmers' calculus" – which results from excessive enamel erosion, making your teeth extra sensitive and appear more yellow. With this in mind, consider toothpaste to strengthen enamel such as Colgate® Enamel Health™ Sensitivity Relief to repair any tooth enamel damage you may already have.
Along with maintaining your pool and keeping its chlorine levels at the recommended level, you can further protect your teeth by keeping your mouth closed when you swim, so that the chlorinated water doesn't come into contact with them as often.
Your dentist is your best resource for additional questions regarding how to protect your teeth during a given sport. He or she can ultimately help you choose the helmet that's most appropriate and create a custom mouth guard to fit your teeth. Wearing a mouth guard for each day of practice might be a pain, but it's a lot more comfortable than dealing with the dental injury that can follow.