The Collaborative International Dictionary of English v.0.48:
Water witch \Wa"ter witch`\ (Zool.) (a) The dabchick. (b) The stormy petrel. [Prov. Eng.] [1913 Webster]WordNet (r) 3.0 (2006):
water witch n 1: someone who uses a divining rod to find underground water [syn: water witch, dowser, rhabdomancer]