Even entities that are not purely astral, but much more complex, need the astral plane as a gate to enter the material plane. Ases As well as I do. Clearly there is reference to names. An old magical idea is that once you know the name of an entity you have it under your control. There is more to that concept of the water.
Water has a clear reference to the etheric level on the material plane where an entity manifests.
This is life energy. Life energy has other names such as prana, chi, orgone, or animal magnetism. I have been able to photograph many entities when I supplied them with an adequate amount of life energy from the Chi generators that I invented. This goes hand in hand with the Voodoo concept that you need to feed the entity that you have do the work. The feeding technique is always a way to set free sufficient amounts of life energy.