undertow

noun

1. the seaward, subsurface flow or draft of water from waves breaking on a beach.
2. any strong current below the surface of a body of water, moving in a direction different from that of the surface current.

noun

1. the seaward undercurrent following the breaking of a wave on the beach
2. any strong undercurrent flowing in a different direction from the surface current

n.1798, from under + tow (n.).

1. An underwater current flowing strongly away from shore. Undertows are generally caused by the seaward return of water from waves that have broken against the shore.