Swimsuits Parade, Sydney, Australia

Germs, bacteria and mold can grow very quickly on wet bathing suits. Medical professionals warn that wearing damp swimwear for long periods of time can cause a number of infections and rashes in children and adults, and warn against sharing bathing suits with others. They suggest changing out of a wet bathing suit right away can help prevent vaginal infections and itching in females and Tinea Cruris "Jock Itch" in males.
History
In Classical antiquity swimming and bathing was done nude. There are Roman murals which show women playing sports and exercising wearing two-piece suits covering the areas around their breasts and hips in a fashion remarkably similar to a bikini of ca. 1960. However, there is no evidence that this was used for swimming. All classical pictures of swimming show nude swimmers.