Guida
Okinoshima Beach is a unique tombolo (a connected island) located in Tateyama City, Chiba Prefecture. Originally a detached island, the 1923 Great Kanto Earthquake caused a geological uplift that changed the landscape, creating a sandbar that connects the island to the mainland. The island is roughly 1km in circumference, and you can walk across a 200m sandbar to reach it. The water quality is exceptional, having achieved the highest 'AA Rank' in the Ministry of the Environment's water quality surveys. This ensures breathtakingly clear, marine-blue waters that sparkle under the sun. As part is of the Minamiboso Quasi-National Park, the area maintains a rich and healthy marine ecosystem.
The topography of this area has a fascinating history. Once a remote island, the geological shifts following the 1923 Great Kanto Earthquake altered the currents and led to the accumulation of sand, creating the current land connection. The island is also home to the Okinoshima Uga Daimyojin Shrine, said to have been established in 1096. Furthermore, the site has historical significance related to the Tokyo Bay Fortress, with remnants of man-made underground bunkers still visible. It is a place where natural shifts and human history are deeply intertwined.
The greatest draw of Okinoshima is its transparent sea and diverse ecosystem. The surrounding waters are known for hosting coral, marking one of the northern limits for coral growth in the region. You can observe coral even in shallow areas, making it an ideal spot for snorkeling and skin diving. The island also boasts lush vegetation such as Machilus and various tropical-looking plants, offering a fascinating botanical environment. At the entrance to the island, a natural tunnel formed by overhanging trees creates a beautiful, scenic gateway.
The beach is primarily open during the summer season (late July to late August). During this period, several 'Umi-no-Ie' (beach huts) operate on the sandy areas to provide amenities. For the best experience, visit during sunny daytime hours when the sunlight turns the ocean into a brilliant marine blue. Additionally, visiting during low tide is highly recommended, as the receding waters reveal tide pools and rocky areas perfect for observing marine life.
Okinoshima offers a variety of nature-based activities. Beyond swimming, you can enjoy exploring tide pools and observing small creatures among the rocks when the tide is out. Snorkeling and skin diving are highly popular due to the presence of coral. On the far side of the island, you can enjoy beachcombing to find beautiful seashells and sea glass washed ashore. For those who prefer land-based activities, there are walking paths to explore the island's rich flora.
The area is part of the scenic Minamiboso Quasi-National Park. Please note that parking is limited to roadside street parking rather than a formal lot. For convenience, there is a Seven-Eleven convenience store on the mainland side before you cross to the island, which is a great place to purchase drinks and snacks in advance. The area is also close to Tateyama Port, making it a great addition to a South Boso sightseeing itinerary.
As this is an uninhabited island, there are no vending machines or restaurants. It is essential to bring your own food and drinks. We recommend wearing swimwear, comfortable walking shoes for island exploration, and a hat for sun protection. To preserve the environment, please ensure that if you flip over rocks during tide pool exploration, you return them to their original position. While lifeguards are present during the official beach season, all activities outside these times are at your own risk.