Deep Blue (ディープブルー Dīpuburū? ) is chapter 1 of Grand Blue manga.
Short Summary[]
In April, Iori Kitahara arrives in Izu to stay with his uncle and attend university. He's shocked when he enters his uncle's diving shop, Grand Blue, and finds it filled with naked, drunk, and muscular men playing Yakyuken. After a series of events, he gets dragged into their antics, including drinking and playing Yakyuken in his underwear. The next day, he wakes up hungover in a lecture hall, having experienced a wild night at Grand Blue.
Summary[]
The chapter opens with a girl in scuba gear swimming in the ocean

Iori arriving in Izu
It's April and Iori Kitahara, who has just arrived in Izu, is picked up by his uncle, Toshio Kotegawa. They drive back to his uncle's diving shop, Grand Blue, where Iori will be staying while he attends university. Iori notices the girl from early emerging from the sea before turning to enter the shop.

Iori's shocking discovery
Upon opening the door to Grand Blue, Iori is greeted by the sight of many naked, drunk, and heavily muscled men playing Yakyuken. In shock he runs out of the shop, only to see two men chasing after him. They drag Iori back to Grand Blue only to have him helping with preparing the diving tanks.
One of the two guys introduces himself as Ryuujirou Kotobuki, a third year student at Izu University in mechanical engineering. He tries to recruit Iori to the diving club. The two then bump into Nanaka, who is coming back from a test dive.

Iori's transformation
They return to the shop where Kotobuki and Tokita admonish Iori for complaining and then coerce him into drinking and playing Yakyuken. Chisa returns to the shop where she sees Iori stripped down to his boxers chugging beer. Upon seeing her, Iori greets Chisa but is rejected with extreme disdain.
After finishing their task with the clean up, Kotobuki and Tokita proceed with coercing Iori into participating in another round of Yakyuken while promising to get him to his first class the next day on time.
The story cuts to Iori in a lecture hall and suffering from nausea and a hangover. A cute girl sitting next to him invites him to a party with her and her friends. However laughter and talking interrupts this dream and Iori awakens to find himself passed out nearly naked in front of the lecture hall.