Corny. That word is the best way to describe this absolute abomination of a show. When you combine all the corny arcs of Gintama, remove the relatable characters and make them just there to be "funny", you get Grand Blue. For 12 episodes, I maybe only laughed once or twice but that is about it. The way they exaggerate things is what pisses me off the most here. It is just so poorly executed.
All in all. Story is non-existent and characters are straight-up trash. 1/10 maybe 0 if I can. Art is pretty decent and the opening is pretty good. I forgot about the ed song though but still story and characters are what matters the most.