You can make it a crab boil, a shrimp boil or a Cajun boil depending ... maybe some cayenne or red pepper flakes if you want a little spice. To the boiling water, either add two bottles of beer ...
You can buy a crab live and boil it yourself; alternatively ... and has heavy front claws with almost-black pincers, a rusty-red or brown shell, and red hairy legs mottled with white.