คิตาฮาระ อิโอริ นักศึกษามหาวิทยาลัยที่ไม่มีเป้าหมายในชีวิต จนได้ย้ายมาอยู่กับลุงที่เปิดร้านขายอุปกรณ์สำหรับนักดำน้ำ Gran Blue ที่ชายหาด
Among the seacoast city of Izu's ocean waves and rays of shining sun, Iori Kitahara is simply starting his freshman year at Izu University. As he moves into his uncle's skin diving look, Grand Blue, he thirstily anticipates his dream school life, crammed with stunning women and smart friends.
But things do not specifically go per set up. Upon coming into the look, he encounters a gaggle of rowdy, naked upperclassmen, UN agency straight off squeeze him into taking part in their alcoholic activities. tho' unwilling initially, Iori quickly provides in and becomes the guts and soul of the party. sadly, this earns him the scorn of his full cousin, Chisa Kotegawa, UN agency walks in at exactly the incorrect time. Undeterred, Iori still vows to appreciate his ideal school life, however can things go per set up this point, or can his scenario take one more dive?