[header] How to clean a blue crab [title] Kill the crab humanely before you remove the shell. [step] If you're using a live blue crab, submerge the crab in a large bowl of ice water for 2-3 minutes to stun it. Then, remove the crab from the ice water and lay it on its back. 
Use a knife or ice pick to stab the crab through its shell 1 inch (2.5 cm) below its mouth. [substeps] You can also boil the crab for 1 minute to kill it.