National Clam on the Half Shell Day is observed on March 31, 2018. The day is a chance to eat clams in a raw way and in their natural packaging. A clam's shell consists of two usually equal halves. Clams can be eaten raw, steamed, boiled, baked or fried. They can also be made into clam chowder or they can be cooked using hot rocks and seaweed in a New England clam bake.