From Bulbapedia, the community-driven Pokémon encyclopedia.
A Swimmer is a type of Pokémon trainer that first debuted in the Generation I games. Originally, they only came in male versions, Swimmer♂ (Japanese: かいパンやろう Swimsuit Guy), but in Generation II, female swimmers, Swimmer♀ (Japanese: ビキニのおねえさん Bikini Lady) were introduced.
They specialize in Template:Type2 Pokémon.
The Japanese versions show the male Swimmers wearing Speedo. This was changed to shorts in the dubs.