Twenty year old Iori Kitahara is about to start his new college life. Excited to make the most of his youth he decides to move in with his uncle who happens to run a scuba diving store named "Grand Blue" nearby. Living together with him were his beautiful cousins Chisa and Nanaka Kotegawa. All seems well until he enters the store and finds a gang of macho guys partying naked and drinking. Amongst them, Shinji Tokita and Ryuujirou Kotobuki turn out to be instructors at the store and also go to the same university. Hearing that he was a new fresher to the uni he ends up relunctantly getting dragged into their Diving Club "Peek-a-boo" club activities. Unfortunately, the club was still lacking members on fresher's day and Iori ends up dragging a classmate along too, Kouhei Imamura, a handsome guy who catches the attention of many women except his open Otaku way of life ends up keeping everyone away from him. As the new semester begins, the odd mix of personalities ends up leading to a variety of weird and awkward situations.

This show revolves around the college life of characters with quirky personalities that leads to some funny or odd interactions during their everyday lives. You've got a bunch of guys that enjoy drinking and being naked while the girls around them treat it as the norm. Nanaka doesn't mind them that way around in the store but she has a sister complex and gets sexually obssessed with anything Chisa has body contact with. Then you've got Tokita and Ryuujirou's friend Azusa from the all women university who happens to be bisexual, energetic and very open minded. The list goes on... The only people that seem to be normal is Chisa who does her best to ignore it all but that doesn't stop her from being dragged into their activities since they're always around. Iori always ends up with the short end of the stick as he becomes friends with the weird bunch and ends up with all sorts of misunderstandings pinned on him.

Sometimes it feels like the jokes are stretching it a bit - a lot of times they don't stray far from macho guys drinking and getting naked or running around in their underwear. However, the jokes do get a bit more interesting in the second half of the show. It also has its rare more serious slice-of-life moments when it's not being silly and fooling around so that the growing Grand Blue gang end up watching out for each other.

There's no shortage of fan service scenes. Character designs are aesthetically pleasing although their angry serious expressions remind me of Attack on Titan. You'll see the girls in swimsuits quite often since it's a scuba diving club... and the naked macho guys. I don't think there's a single episode where the guys don't strip naked or are at least half naked - it's the norm for the guys. And where there's alcohol involved in any story there's usually sex too and the show isn't afraid to make a joke of out it either. Certain scenes can be... brutal. As for the music, I didn't find anything that stood out other than the odd karaoke style ending theme although, the OP "Grand Blue" fits in with the stereotype image of summer - blue skies, blazing sun and going all out with passion.

It's a weird lively summery, slice-of-life comedy show full of nudity aimed at the young male adult audience, with the odd serious moments that barely touches on scuba diving. It's all about drinking and partying nude - your whole summer YOLO attitude. At least after watching this you'll be a bit more knowledgeable about scuba diving if you weren't already and know what an "Old Man" or "Hamasaki's Wife" can mean in Okinawa from episode 11.