Amanchu!

Other titles: あまんちゅ!

The hyperactive teenage scuba diver, Hikari Kohinata, lives in a small town near the sea. On her first day of high school she meets the shy transfer student, Futaba Oki, who is struggling to find a place after moving away from Tokyo. Hikari takes the lead, dragging Futaba into her hijinx, and the two soon become close friends