S01E01 Churaumi!
This introduces the characters and the setting. On the beach, Momoko Orizuka and Kaname Okiura are relaxing when a houseboat comes in. On that houseboat is Amuro Ninagawa. She is holding a three-foot long shark...
Amuro gets chosen to replace Momoko in the relay squad. Masa attempts to replace Momoko by dressing in drag, but the team tells him no. The rest of the races are run.
Kaname Okiura, a student of Umineko Shougyou High ("Umishou" for short), joined the school’s swimming club in order to learn how to swim, but the club is filled with weirdos. Then, a sunny, happy-go-lucky girl named Amuro Ninagawa who transferred from Okinawa joined the club. Her extraordinary underwater speed and unorthodox swimming style surprised every club member, especially Okiura, because she reminds him of a mermaid he saw only once in his early childhood.