[noun] [U] - a strong current flowing under water in a different direction to the way the water on the surface is moving, esp. the strong current that flows under water away from the land at the same time as a wave hits the beachOn some beaches the undertow is dangerous because it can pull swimmers out into deep water.
UNDERTOW
Meaning of UNDERTOW in English
Cambridge English vocab. Кембриджский английский словарь. 2012