No need. Crab is a crustacean seafood, breathing mainly depends on the gills on both sides, which can store more water. When the crab leaves the water and enters the land, the water and air in the gills will spit out together to form bubbles, which proves that the crab breathes without extra water. If you add water, it will hinder the crab's breathing because there is too much water, so that the crab will die of hypoxia and suffocation.

Extended data:

Crab is a crustacean, belonging to the mollusk class Decapoda. Its body is protected by a hard shell and it breathes through its gills. Taxonomically, it is the same kind of animal as shrimp, lobster and hermit crab. Most kinds of crabs live in the ocean or offshore areas, and some live in fresh water or land. Common crabs are Portunus trituberculatus, Portunus trituberculatus, Eriocheir sinensis and Eriocheir sinensis (Eriocheir sinensis, Eriocheir sinensis and Eriocheir sinensis).