A rock that does not allow water to flow through it is called impermeable.

Here are some other terms that describe this property:

* Non-porous: Meaning it has no spaces or holes for water to pass through.

* Dense: Meaning the rock is packed tightly with little to no open space.

Examples of impermeable rocks include:

* Granite

* Basalt

* Marble

* Shale

Let me know if you have any other questions!