Hydromancy is the power to spy on other people and view distant places using water. Hydromancy is a form of Divination.
Witches and warlocks that possess this power are able to see and possibly hear everything that is going on with a specific person or place they wish to spy on at that given moment. As seen with Penelope Gardiner, when a witch or warlock uses this power, this power shows an aerial view of the specific person(s) or place they're spying on. Hydromancy can be used by any water such as a pond, the ocean, or in a puddle of water. Penelope Gardiner is the only known witch to have this power.
- Penelope used this power to spy on the Beauchamps and keep watch over them.
- In a deleted scene from Electric Avenue, whilst using this ability, Penelope throws a rock into the water and it falls from the sky, narrowly missing Joanna and Wendy.