Tenjin-jima Marine Biological Garden protects the natural environment of the Miura Peninsula's representative coastline. The hamaomoto (hama-yu) of Tenjin Island was designated a natural monument of Kanagawa Prefecture in 1953, and in 1965, part of Tenjin Island, as well as Okinokasa-shima and the surrounding waters, were designated as scenic and natural monuments. At the Tenjin Island Visitor Center, you can learn about the history and annual events around Sashima and Tenjin Island, local fishing methods, and village life. There are also specimens of plants, seaweed, seaweed, insects, and shellfish, as well as the Kuroshio Current flowing into Sagami Bay.