Mystery Bay State Park is an eighteen-acre (7.3 ha) marine state park on Mystery Bay, in Jefferson, Washington, United States that offers picnicking, shellfish harvesting, fishing, boating, beachcombing, and scuba diving..
Mystery Bay State Park is an eighteen-acre (7.3 ha) Washington marine state park on Mystery Bay, a small inlet off Scow Bay/Kilisut Harbor on the western side of Marrowstone Island. Jefferson, Washington, United States Park activities include picnicking, shellfish harvesting, fishing, boating, beachcombing, and scuba diving. 
