whirlpool

a powerful circular current of water (usually the result of conflicting tides)

An eddy or vortex of water; a place in a body of water where the water moves round in a circle so as to produce a depression or cavity in the center, into which floating objects may be drawn; any body of water having a more or less circular motion caused by its flowing in an irregular channel, by the coming together of opposing currents, or the like.