There isn't much of a story. The principal and Saito found a chest full of bikinis (don't ask how) and decided that everybody should go to the beach for a short 2-day vacation.
(girls + bikinis) x (Order of Perverts + Principal) = you know what happens.
Oh, and add a giant octopus with tentacles in that equation as well.
It was a great, hilarious OVA that everybody should watch just for the laughs. It's definitely worth 20 minutes of your time, so enjoy it!
