Here's why:
* Gills: Water hermit crabs, like all crabs, breathe through gills. Gills need to be constantly moist to function properly. On land, the gills would dry out quickly, leading to the crab suffocating.
* Water Dependency: Water hermit crabs are adapted to living in saltwater environments. Their bodies require the salinity of seawater to maintain proper hydration and bodily functions.
* Shell Requirements: Land hermit crabs typically have thicker, more robust shells that can withstand drier conditions. Water hermit crabs have shells adapted to life in the water, which are not suitable for land living.
Important Note: While water hermit crabs are fully aquatic, there are many land hermit crab species. These land hermit crabs can survive out of water for extended periods, but they still require access to moisture and a humid environment.