Mystery Bay State Park is a 10-acre (4.0 ha) Washington marine state park on Mystery Bay, a small inlet off of Scow Bay/Kilisut Harbor on the western side of Marrowstone Island. The park is located approximately one half mile north of the Nordland General Store (which also faces Mystery Bay) on Flagler Road (SR 116). Many older wooden sailboats can be swinging at permanent moorage at the park.