1 bushel (about 8 dozen) live Maryland blue crabs, preferably large. (NOTE: Males are usually larger.) A bushel is enough for 2 to 3 pots of crabs, depending on their size.
2 (12-ounce) cans beer
4 cups water
1 (8-ounce) packet crab boil seasoning, usually available where crabs are purchased
2 sticks butter, melted (optional)