WordNet (r) 3.0 (2006):

riptide
    n 1: a stretch of turbulent water in a river or the sea caused
         by one current flowing into or across another current [syn:
         rip, riptide, tide rip, crosscurrent,
         countercurrent]
    2: a strong surface current flowing outwards from a shore [syn:
       riptide, rip current]

Moby Thesaurus II by Grady Ward, 1.0:

37 Moby Thesaurus words for "riptide":
   direct tide, ebb, ebb and flow, ebb tide, flood, flood tide, flow,
   flux, flux and reflux, full tide, high tide, high water, low tide,
   low water, lunar tide, neap, neap tide, opposite tide, refluence,
   reflux, rip, solar tide, spring tide, thalassometer,
   tidal amplitude, tidal current, tidal current chart, tidal flow,
   tidal range, tide, tide chart, tide gate, tide gauge, tide race,
   tide rip, tidewater, tideway