Kitahara Iori looks forward to his new life on the Izu Peninsula as he prepares to start his college life there, staying in a room above his uncle's diving shop "Grand Blue." However, he is quickly shocked as he meets the local Diving Club, a group full of buff men who spend more time drinking, partying, and stripping naked than actually diving. Despite his attempts to distance himself from the group, Iori gets quickly swept up in their antics, while his cousins try to show him the wonders of diving into the ocean and sea.