Tarai Current

The Tarai Current is a giant whirlpool that connects the World Government's three major facilities: Enies Lobby, Impel Down and the Marine Headquarters. This current allows World Government and Marine ships to move between the three locations privately. It is located on the Grand Line in a corner where the adjacent Calm Belt and Red Line intersect. The three facilities form a triangle that surrounds the current. The only way to access the current is to enter through a facility's Gate of Justice. The "sides" of the triangle have several small currents that would sweep away any ship that tries to bypass the Gates and access the Tarai Current directly. On the other hand, any ship already inside the current would continually stay in it unless a Gate of Justice was opened to let it in.

The Viz Manga and FUNimation subs call this the Tub Current.