Abyss School

Yuhee, an ordinary girl at a private school, picks up a bright purple conch shell on the beach before dozing off on the school bus. She wakes to find her school has sunk into the deep sea, surrounded by cult-like followers of a high priest called the Abyss. She must solve puzzles, evade terrible monsters, and navigate an alien underwater world to escape Abyss School and return home.