Orenchi no Furo Jijo

*The Second OVA of Kono Dan series. They say look before you leap and make sure you can swim before you go in the deep water, but when a picture of his late grandfather falls into the ocean, Shima jumps in after it without thinking. Nearly drowning as a result, he is instead saved by a very perfect stranger... one whose strangeness extends to only being human from the waist up! For Shima, who's always felt like a fish out of water himself, it's more than just a revelation, and the young man and merman quickly begin to bond in ways neither anticipated. And yet, it's going to be far from easy sailing. After all, Shima and Isaki aren't just from opposite sides of the tracks, they're from entirely divergent species, and swimming in separate gene pools may make maintaining a long term relationship a whole different kettle of fish!

One day, Mukoujima Takurou, a boy in high school who loves fishing, catches a pig tailed mermaid called Muromi-san who speaks in the Hakata dialect. She comes to visit Takurou often, along with her fellow mermaids Sumida-san, Fuji-san, Levia-san, Hii-chan, and even some other fantastical creatures such as Yeti and Harpy!

Michishio Nagasumi's life couldn't be any more normal. In an odd twist of events, during his summer vacation he ends up almost drowning in the sea. Luckily, the cute mermaid Seto San appears to save him. However, San is from a yakuza mermaid family and according to their law, if a human is to catch sight of a mermaid, either he or the mermaid must die. The only other way is for Nagasumi to be taken in as a family member, marrying San. In attempts to save both of their lives, Nagasumi asks for San's hand in marriage. Nagasumi's summer vacation reaped more then what he would expect, as he must now protect San from others finding her secret out.

Kaname Okiura, a student of Prefectoral 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, let alone who can teach him swimming. 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 (plus her personal habit of nude swimming—a powerful magnet to teenage boys) surprised every club member, especially Okiura, because she reminds him of a mermaid-like creature he saw only once in his early childhood.