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Four Blues is the term used to refer to the four cardinal seas of the Blue Sea, making up most of the world's surface.


The Four Blues exist as four separate oceans due to the presence of the Red Line and the Grand Line. Due to the latter being bordered by the Calm Belt and the former having a nigh indestructible structure, along with a towering size, it is almost impossible to travel from one Blue to the other.

Their waters, while still spelling danger and peril, work in pretty regular patterns, requiring only a normal compass to be able to be traveled through.


North Blue, hailed as the strongest Blue, is a sea that harbors many pieces of literature and a good quantity of military organizations.

South Blue is known for its exotic and odd findings, including its flora, fauna, and customs.

West Blue is a sea renown for its organizations and Underworld-like activities.

East Blue, considered the weakest of the Four, borders the Red Line on the left and the Grand Line on the right.



  • Even when not counted together, each of the Blues stand for the biggest water-based oceans in the entire world.