Kumejima Open Water Swim

The Kumejima Open Water Swim is an open water swimming race held in the open sea off the shores of Oujima Coast, in the island municipality of Kumejima in Okinawa, Japan. Swimmers gather on the tide-washed coastline of Oujima, entering the warm Pacific swell for a weekend of racing across an exceptionally clear marine basin. The event provides a broad menu of open water challenges, staging individual courses over 400, 800, 1,500, 1,600, 3,000, 5,000, and 10,000 meters. Every race gets underway together through a simultaneous water start, sending swimmers off into the rolling saltwater from an in-water line. While traditional swimwear is standard, wetsuits are permitted for participants who submit an advance request to the secretariat. Held across two days in October, past editions such as 2013 highlighted the event as a celebration of one of Okinawa's most alluring island settings, defined by inviting, luminous ocean water.

Tatami-ishi: the volcanic turtle-shell rocks of Oujima

The starting grounds lie on Oujima, a small island positioned 500 meters off the eastern flank of Kume Island. Before a road bridge connected the two shores in 1983, islanders crossed the strait on foot at low water, or relied on stilts and wooden fishing boats when the tide rushed back in. That same tidal rhythm reveals the coast's most extraordinary natural landmark along the south shore, about four kilometers from the race area. Here lies Tatami-ishi, an ancient formation of approximately one thousand tightly fitted pentagonal and hexagonal stone columns. Created roughly twenty million years ago during the Miocene period, the rocks took shape as molten andesite lava from an erupting volcano cooled, contracted, and cracked into geometric prisms. Spreading across the tidal flat like the giant shell of a sea turtle, the 29.3-hectare site was chosen as one of the 100 Geological Sites of Japan in 2007 and protected as a national Natural Monument in 2014.

Hate no Hama and Oha Island: shifting sands and reefs

Beyond the race shore, an expanse of 119 square kilometers of surrounding sea and land is safeguarded as the Kumejima Prefectural Natural Park. Five kilometers east of Kume Island rises Hate no Hama, a seven-kilometer stretch of sandbars composed entirely of sand without trees or soil. The formation comprises three separate sand islands—Maanu Hama, Nakano Hama, and Hatinu Hama—encircled by extensive coral reefs where glass-bottom boats navigate the turquoise shallows. Depending on the flow of the tide, swimmers and visitors can walk directly across the exposed sandbars between the dunes. Just 400 meters east of Oujima sits neighboring Oha Island, fronting the edge of this vast sand system. While the dredged channel between Oha and Oujima contains deepened passages where boat currents run fast, spring tides drop the water so dramatically that a 200-meter sandbar emerges across the strait, allowing anyone to stroll across between the islands in just ten minutes over calm, sunlit flats.

Sunken Ryukyu tribute ships and the cliffs of Gushikawa

Kume Island has witnessed centuries of seafaring commerce, serving historically as a critical navigational stopover for Chinese envoys known as sapposhi voyaging to the Ryukyu Kingdom. Beneath the surface off the shores of Oha Island and Nakano Hama lie the submerged shipwrecks of ancient Ryukyu tribute ships and merchant vessels. Marine archaeological surveys have brought up celadon ceramics, delicate white porcelain, stone weights, and massive wooden ship anchors preserved in the seabed sands. In 2011, Oha Island even hosted the very first underwater cultural heritage tour in the Nansei Islands, inviting divers into its maritime museum under the waves. Looking out over these ancient sea lanes from the land, the ruins of Gushikawa Castle crown a rocky promontory about five kilometers from the race venue. The fortress perches atop steep coastal precipices dropping straight into the East China Sea on three sides.

Ara Beach foraging and the Oujima Haarii races

On the southwestern coast of Kume Island, roughly one hundred kilometers west of Okinawa's main island, Ara Beach reveals another dimension of local water culture. Natural freshwater springs trickle directly into the sea here, fostering an unusually rich gathering ground for fish and shellfish. During extreme spring low tides, the ocean retreats so far that beachgoers can walk a full kilometer offshore across the exposed sea floor to reach the outer barrier coral reef. Along these rocky tidal shallows, island fishermen wade through the quiet pools with baskets to harvest octopuses and shells as the sun sinks over the reef edge. That deep connection to the water culminates back at Oujima's own fishing port in early June, when islanders celebrate the traditional Haarii dragon boat races.