Hydromancy
Hydromancy (Greek hydro, water) is divination by water: ripples, reflection, color, sound, behavior of objects dropped in it. Ancient practice in Mesopotamia, Egypt, Greece. The famous "cup of Joseph" of the Bible (Genesis 44:5) is a hydromantic reference.
Methods
Mirror water (catoptromancy variant), water with oil drops (modern Latin American practice), water under moonlight, water with floating objects.