Swimmer's Eat is the result of a water build-up in the outer canal of the ear that causes infection.
It can largely be avoided by swimming for just an hour or less at a time, by using earplugs, and by thoroughly drying out you ears after a swim.
If infected, doctors suggest using a cotton ball dipped in a combination of water and vinegar to treat the infection.
Pain can been alleviated by applying a hot water bottle to the ear, and by taking ibuprofen.