Blue crabs can't be eaten when they are dead. The bacteria in its body will multiply, and then it will decompose crab meat and secrete toxins. So if people eat this dead blue crab, they may have food poisoning, nausea, vomiting, abdominal pain, and even severe shock.
Besides being dead, blue crabs can't be eaten overnight. If seafood is eaten overnight, it will produce protein degradation products, which will damage the liver and kidney function, so blue crabs should not be eaten overnight.
Except for blue crabs, fish, vegetables and other seafood are not allowed to eat. Eating these foods overnight will do some harm to your health. I suggest you not be willful.