2. When cooking crabs, be sure to put cold water in the pot, so that the crab legs are not easy to fall off. Because crabs grow in mud, they often carry some toxins in their bodies. In order to prevent these pathogenic microorganisms from invading the human body, they must be steamed and cooked thoroughly when eating crabs. According to the size of crabs, it is appropriate to cook for 8- 10 minutes after the water is boiled, and the meat is cooked but not too rotten.