Freshman Iori Kitahara moves to the coastal town of Izu to start his college life, staying at his uncle's scuba diving shop, "Grand Blue." He arrives with high hopes of a "sparkling" university experience filled with beautiful girls and academic success. However, his dreams are immediately shattered when he walks into the shop to find a group of buff, naked upperclassmen in the middle of a rowdy drinking party.*

Despite his initial resistance, Iori is quickly sucked into the "Peek-a-Boo" Diving Club—a group that seems to spend far more time chugging "Oolong Tea" (which is actually 90% vodka/whisky) and stripping down to their boxers than actually diving. Along with his fellow victim and otaku classmate Kohei Imamura, Iori navigates the absurd, alcohol-fueled chaos of college life while occasionally—just occasionally—learning to appreciate the genuine beauty of the ocean.