Amanchu! ~Advance~

Hikari Kohinata and Futaba Ooki have together found joy in many things through scuba diving and the most everyday of events. Hikari was born and brought up in a small oceanside town on Izu, and Futaba moved there from Tokyo, but the two polar opposites met at Yumegaoka High and instantly hit it off. The always-reserved Futaba found her perfect foil in the cheery and optimistic Hikari, and their friendship gave her the courage to take the first step and experience many of the smaller joys in life. She also took the Open Water Diver exam and passed, and now she has her sights set on the Advanced Open Water Diver certification.

Synopsis from Anime News Network