Fishman Island is the home of the fishmen and merfolk. It serves as an underwater gateway to the New World for those who do not wish (or are not legally permitted) to cross over the Red Line above. Though it is literally directly under the main seat of power of the World Government, it is unguarded by marines and is pretty much left alone by the World Government even though it is known to have active acces for pirates and revolutionaries alike. It is also notoriously difficult to reach, with only 30% of the ships surviving the journey. It is encased in a giant bubble, allowing human visitors to breathe. For World Nobles, it is also one of the few places in the world where their ability to summon a Marine Admiral as they please is not so easy to accomplish.

Thus, Fishman Island is virtually one of the best places to go for a hit on a Celestial Dragon because of the delayed consequences that are called upon.