Iori Kitahara relocates to the seaside village of Izu for his first year of university, living above Grand Blue, his uncle's scuba diving business. Iori has great expectations and aspirations of having the perfect college experience, but when he enters the store, he gets lured into the drunken antics of the carefree Diving Club members that frequent the area. Iori grudgingly attends their weird party after being persuaded by upperclassmen Shinji Tokita and Ryuujirou Kotobuki. Chisa Kotegawa, his cousin, later walks in and catches him in the act, earning Iori's scorn. Grand Blue, based on the renowned comedic manga by Kenji Inoue and Kimitake Yoshioka, depicts Iori's antics with his quirky new pals as he seeks to attain his ideal college dream, while also learning how to scuba dive.