Detective Conan OVA 7

Koumi Island, a picturesque spot in the Pacific Ocean, is steeped in a time-honored legend. Locals have long shared tales of the Seabed Palace, an ancient underwater ruin said to house the treasure of two historical female pirates, Anne Bonnie and Mary Reed, who lived three centuries ago. During a holiday visit to Koumi Island, Conan and his friends encounter a group of treasure hunters whose behavior raises their suspicions.