Mouthguard maintenance:

•           Brush teeth before wearing a mouthguard.

•           Never share a mouthguard with teammates.

•           During sporting events, have a backup mouthguard.

•           Purchase disposable mouthguards.

•           Clean mouthguards before storing them.

Swimmers Risk Stained Smiles, Chipped Teeth

"Competitive swimmers may be at risk for developing yellowish-brown or dark-brown stains on their teeth, reports the Academy of General Dentistry (AGD), an organization of general dentists dedicated to continuing dental education..." 

Full Article

Avoid Diver's Mouth Syndrome When Scuba Diving

"Before you go scuba diving, see your dentist because this sport can lead to jaw joint pain, gum tissue problems or tooth pain.

All of these symptoms add up to "diver's mouth syndrome," a condition that is caused by the mouthpiece and by the air pressure change involved in scuba diving – a sport that is enjoyed by about 4 million enthusiasts in the United States...."

Full Article

I hope this information is benefical and please leave your comments if you would like to add anything.