Portunus can't be kept in fresh water for one night. Portunus trituberculatus is a kind of seawater crab, which can only survive for 2~3 hours in fresh water. Portunus likes the cold environment. When the temperature is between 0℃ and 6℃, the swimming crab will stop eating and go to sleep. If swimming crabs want to be preserved for a long time, they can be fed some food and put in the fresh-keeping layer of the refrigerator.

When swimming, the swimming crab stands upside down in the water. Step five, the feet swing frequently to swim horizontally or directionally. When diving into the mud and sand, it often forms an angle of 15~45 degrees with the bottom of the pool, and only the eyes and tentacles are exposed.