hydromancy
Divination by water or other liquid.
uncountable
Hydromancy is the supposed art of divining by water. The Persians, according to Varro, invented it; Pythagoras and Numa Pompilius made use of it; and we still admire the like wonderful prognosticators.
Where it comes from
From French hydromancie or Late Latin hydromantia, from Ancient Greek ὑδρομαντεία (hudromanteía); corresponding to hydro- + -mancy.
Adapted from the Wiktionary entry hydromancy (CC BY-SA 4.0).