Here's why:

* Central Vacuole: In plant cells, there's a large, central vacuole that takes up most of the cell's volume. It's filled with water and dissolved nutrients, providing turgor pressure that helps the plant stand upright.

* Smaller Vacuoles: Animal cells have smaller vacuoles, but they still play an important role in storing water, as well as other substances like waste products and enzymes.

While other cell structures, like the cytoplasm, contain water, the vacuole is the primary storage location for water in a cell.