as dark as night
2.".., the sea is as dark as if an ink stick had been rubbed on its surface, and many hundreds of eddies can be seen floating downstream in succession. " Just as described the book titled Hachijo-Hikki written by a Japanese Uda, the Kuroshio-the western boundary current in the North Pacific, polewardly transporting huge amounts of warm water day and night, plays an important role in the mass and heat balance in the gyre.

