Claim: 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..
Evidence: 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.