Okinoshima Beach

At Okinoshima Beach in Tateyama, instead of a typical stretch of coast, you get a sandy pathway leading straight to a small uninhabited island, a landform created after upheaval from the 1923 Great Kanto Earthquake helped turn what had been a separate island into a walkable sandbar. The island itself is only about 1 kilometer around, but it packs in a surprising mix of beach, forest, exposed rock, and quiet coves. 

What makes Okinoshima especially memorable is the contrast between its gentle family-friendly shallows and the richer natural life just beyond them. The main swimming area is known for calm, shallow water, and official tourism sources consistently describe it as a strong spot for swimming, snorkeling, and shell collecting. The sea around Tateyama is also influenced by the Kuroshio Current, which helps support coral growth at one of Japan’s northern limits, so even near shore you can find a surprisingly vivid marine scene with coral, small tropical fish, and rocky shallows that are great for casual exploration. 

On land, the mood shifts quickly from open seaside to something much more tucked away. The island is covered in dense coastal forest with native warm-climate vegetation, and the paths inside feel half wild, half quietly historical. There is also a small sacred presence here in the form of Uga Myojin [宇賀明神], and parts of the island still hold traces of wartime excavation, including man-made cave-like shelters that survive as subtle reminders of Tateyama’s strategic position near the mouth of Tokyo Bay. It gives Okinoshima more depth than a simple beach stop. 

Along the island’s rocky edges, you’ll come across a few small caves and tunnel-like openings, some formed naturally and others shaped during wartime as simple shelters. They’re unlit and modest in scale, but add a slightly mysterious, historical layer to the otherwise relaxed coastal setting.

For visitors, that mix is really the appeal. You can spend part of the day swimming in the protected bay, then walk across to the island for beachcombing, tide-pool wandering, and a short forest walk with wider views over Tateyama Bay. It is also very photogenic, especially when the pale sandbar curves toward the tree-covered island and the water turns clear blue in strong light. For photos, morning usually gives cleaner light and clearer color in the shallows, while later in the day the sandbar and rocky edges can feel softer and more atmospheric.