Dig a 4-foot diameter hole in the sand. The hole should be deep enough to hold rocks and the food, approximately six to 12 inches deep, depending on the size of the rocks you use.
Collect rocks from the beach, and place two layers of rocks in the bottom of the hole. Make the layers as even as possible. The rocks will reflect the fire's heat to cook the food evenly from the bottom.
Place a layer of driftwood into the fire pit, add newspaper and light it with matches. The newspaper will begin to burn and will catch the driftwood on fire. Allow the fire to build for an hour and a half.
Rake the fire to remove the burned wood, and cover it with a layer of seaweed from 5 inches to 2 feet thick. Wrap vegetables such as corn, potatoes or onions in aluminum foil.
Layer the food into the fire, starting with shellfish such as shrimp or clams. Layer in vegetables. Place the live lobsters on the top layer, and cover the food with seaweed.
Cover the fire pit with a canvas tarp, and allow the food to cook for approximately one hour, or until the lobsters have changed to a red color and any shellfish have opened.