User blog comment:Kaido King of the Beasts/Baseless Predictions/@comment-5391752-20140522023440

There are 7 Seas in the world. We know of the 4 Blues, the Grand Line, and the White Sea. The last one is the Red Sea - a magma ocean beneath the earth. The access is somewhere near (you've guessed it!) Raftel. Crossing it is the only way to go around the world.