Here's why:
* Crabs: Crabs use gills to breathe underwater. However, they also have a specialized adaptation called branchiostegal lungs which allows them to breathe air for short periods of time when they are out of water.
* Coconut Crabs: Like crabs, coconut crabs use gills to breathe underwater. They also have modified gills that can hold moisture and allow them to breathe air for extended periods of time.
This adaptation makes both crabs and coconut crabs highly adaptable to living in both aquatic and terrestrial environments.