Embarking on his freshman year at an Izu coastal university, Iori Kitahara settles in above his uncle's scuba shop, Grand Blue. Fueled by aspirations of a perfect college life, Iori's plans take a wild turn upon encountering the spirited Diving Club members and their boozy escapades. Coaxed by seniors Shinji Tokita and Ryuujirou Kotobuki, Iori gets swept into their offbeat revelries. Things escalate when his cousin Chisa Kotegawa catches him in the midst of the chaos, leading to her disapproval. Adapted from Kenji Inoue and Kimitake Yoshioka's comedic manga, Grand Blue tracks Iori's uproarious escapades with his quirky circle, as he chases his college ideals alongside mastering the art of scuba diving.