Calm Belt

From One Piece Encyclopedia

The Calm Belts are the areas just north and south of the Grand Line. These areas almost never have ocean currents or winds blowing, and are also nesting grounds for Sea Kings and only the really big ones. They are very effective barriers for those trying to enter the Grand Line. The same group of Sea Kings during the Apis saga that previously appeared in the Calm Belt appeared again during the Dead End race and catching the Strawhat Pirates on top of one of their heads again (they got away with the same method as last time, pulling the nose hair on the largest one to make it sneeze them away) which implies that they don't stay in the calm belt consistently.

However it was revealed that the Marines crossed the Calm Belt by using the Seastone lining at the bottom of the ship where a Sea King won't notice a ship above them.

First Appearance: Chapter 101; Episode 54