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The Irie Waterway is a shallow, narrow body of water separating Irabu Island and Shimoji Island, forming a unique natural environment alongside the surrounding landscape. This area is composed of several small inlets and features a distinctive terrain rarely seen elsewhere in Okinawa, offering visitors a striking and memorable natural experience.
The surroundings of the Irie Waterway are largely covered with Ryukyu limestone, remnants of ancient uplifted coral reefs. Along the shoreline, you’ll find wave-cut cliffs and scattered rocks. One of the most remarkable aspects of this area is the presence of mangrove forests in a non-estuarine zone—a rare phenomenon. While mangroves typically thrive in estuaries where freshwater meets seawater, here they grow in a uniquely balanced mix of saltwater and freshwater, creating a distinct ecosystem.
Additionally, the groundwater level around the Irie Waterway is extremely low, allowing freshwater to exist as a lens floating on the denser saltwater—a phenomenon known as a freshwater lens. This rare hydrogeological feature is closely linked to the area’s natural conditions and supports the rich biodiversity of the Irie Waterway.
The bridge connecting Irabu Island and Shimoji Island spans this very waterway. While many may cross it without a second thought, it is actually a hidden sightseeing spot. Known for its panoramic beauty, the bridge offers breathtaking views of emerald-green waters and the blue sky, especially on clear days. Walking across it, visitors can look down at the crystal-clear sea beneath their feet and hear the gentle sound of the waves, giving the impression of strolling above the ocean. At sunset, the scene becomes even more magical, with the bridge and ocean bathed in golden light, captivating all who pass.
This bridge is more than just a passage—it is a special place where visitors can fully appreciate the natural beauty of both Irabu and Shimoji Islands. It is a spot not to be missed during your travels.
Designated as the Irabu Prefectural Natural Park, this area is ideal for enjoying its abundant nature and distinctive landscape. Highlights include features like Toriike, a pair of ponds formed from the collapse of a limestone cave on Shimoji Island, and the dense coastal vegetation of pandanus and Scaevola plants, all of which showcase the profound beauty of Okinawa’s natural world.