The kings of Israel can only be anointed standing over water. Studying Torah by a stream ensures that one's memorization will "flow like a river. (Horayot 12a)." According to Eccl. Rabbah 3:15, if one intends to use the Name of God for theurgic purposes, one should only do so over a body of water (also see Sefer Tagi).
Though God has tamed them, the waters still possess great and destructive power. Therefore, the appearance of supernal water while ascending through the palaces of heaven was considered a barrier and a danger to the living soul. (Chagigah 14b).
By the same token, water is a place of revelation (Ezek. 1:1; Dan. 10; Baruch III, I Enoch 13:7; Kohelet Rabbah 3.16). In the mystical book the Vision of Ezekiel, the prophet received his prophetic insights by gazing into the reflection on the river Chabar. Likewise, German Pietists would perform theurgic rituals over water (Sefer ha-Malbush). Among the Merkavah mystics, some rituals of drawing down angels required the summoner to be immersed neck-deep in living waters. Perhaps the image of the angel appears in the reflecting surface. Some Jewish divination techniques include studying the patterns of oil poured into a bowl of water.
Water sources are a favorite lurking place for spirits and demons (Lev. R. 24.3; Pesachim 112a), a belief that appears to be a hold-over from pagan traditions (The Banyas rapids at the headwaters of the Jordan are named for the Greek God Pan and the ruins of a shrine to him is still visible there).
Magical uses. Without question the water that has the greatest power is mayyim chayyim, "living water." This is rainwater that has not yet been drawn from its source by human hands or by artificial conduit. All seas, natural lakes, rivers, and ponds are reservoirs of living water. A source of living water is also the necessary ingredient in a mikvah, or ritual bath. The potency of living water derives from the fact that it has fallen directly from the pure state of heaven. As such, immersion in it has the power to purify that which it contacts. It also has heavenly energy, and for this reason it is used in rituals of power, such as constructing a golem, divination, ordeals, and the preparation of amulets.