A study has found four in 10 people who go diving recreationally suffer dental problems, from jaw pain to loosened crowns and broken fillings.
The fluctuations in pressure underwater build in the air pockets at the roots of the teeth, causing some divers to surface with broken and shattered molars.
This is made worse by inexperienced divers who clench their teeth against their mouthpiece because of the cold water or stress of learning a new activity.
The study is one of the few to look at people who dive recreationally, on holiday in the Bahamas or Maldives for example, rather than those who do so for work, such as trained military divers. It surveyed 100 adult divers, of whom 41 reported dental symptoms.
More than two in five experienced 'tooth squeeze', or barodontalgia, which is caused by a change in air pressure and also affects air crew and frequent flyers.
When someone descends below the water surface, the pressure builds in walled spaces such as teeth and sinuses.
Divers have reported pain in their teeth from depths of 33 feet to 80 feet, usually in their upper teeth and on their descent.
Full porcelain crowns have been reported to shatter at a dive of 65 feet. Almost one in four certified recreational scuba divers said they suffered pain from their mouthpiece.
This came from gripping the regulator, which provides air on demand, too tightly, leading the study authors to suggest customised mouthpieces, which often come in one size only, could help.
Another 22 per cent of those surveyed reported jaw pain, with five percent noting that their crowns were loosened during a dive, and one person reporting a broken dental filling. Molars, the teeth at the back of the mouth, were most often affected.
The study concludes that recreational divers should consider consulting their dentist before taking the plunge.
With scuba diving ever more popular, and the Professional Association of Diving Instructors certifying more than 24 million people worldwide, it is also suggested that dental health should be assessed before people dive.
Recreational divers are believed to suffer dental problems even more often than military and professional divers.