water witch

noun
1.
Also, water witcher. a person skilled at water witching; dowser.
2.
a witch believed to haunt lakes, ponds, etc.
Origin
1810-20, Americanism

water-witch

[waw-ter-wich, wot-er-] /ˈwɔ tərˌwɪtʃ, ˈwɒt ər-/
verb (used without object)
1.
to practice water witching; work as a water witch.
British Dictionary definitions for water witch

water witch

noun
1.
a person who claims the ability to detect water underground by means of a divining rod