Combine water, vinegar, mustard, pepper, and coriander in a large stockpot with a tight fitting lid, stirring until well combined. Place a rack in the bottom of the stockpot, and bring mixture to a boil. Add crabs; cover and steam 20 minutes or until crabs turn bright red in color.
Remove crabs to a large platter; serve with Cocktail Sauce.
Oxmoor House Homestyle Recipes