Amanchu!

Amanchu! (あまんちゅ！) is a Japanese manga series written and illustrated by Kozue Amano, which began serialization in Mag Garden's Monthly Comic Blade magazine from November 2008. An anime television series adaptation by J.C.Staff aired in Japan between July and September 2016.

Plot
Futaba Ooki, a shy girl who just moved in from the city to the oceanside town of Shizuoka, meets Hikari Kohinata, an erratic girl who loves scuba diving. Together, they join their school's Diving Club and discover the joys of underwater exploration.