- undertow
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/un"deuhr toh'/, n.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.[1810-20; UNDER- + TOW1]Syn. 2. UNDERTOW, UNDERSET, RIPTIDE are terms for a usually strong undercurrent in the ocean, contrary to the direction of surface water. UNDERTOW and another nautical term, UNDERSET (a set or current contrary to the general set of the water, or contrary to the wind), came into notice early in the 19th century. The former is still in general use along the Atlantic coast; the latter now less well known. RIP, in use in the U.S. by the late 18th century, properly means a violently disturbed place in a body of water, usually by the meeting of opposing tides. Of recent years, in the form RIPTIDE, it has also been used, esp. on the Pacific coast, to mean much the same as UNDERTOW, dangerous to bathers where heavy surf prevails.
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a strong seaward bottom current returning the water of broken waves back out to sea. There is in fact no such current in a gross sense, for the overall flow of surface water toward the shore in a surf zone is very small. The water actually thrown up on the shore by breaking waves does flow back, however, and under certain circumstances this return flow may be experienced by swimmers as a strong current. Returning water may, for example, be channelized by the presence or form of obstacles on the bottom into rip currents (rip current) of significant velocity but quite narrow lateral dimension. Also, since the volume of returning water varies with the size of the waves, the swimmer who waits for a low-water trough or a cycle of low waves before standing up to walk to shore may encounter the return flow from large waves just gone by and again experience a seemingly strong current.* * *
Universalium. 2010.
