Tori-Ike Connected Lakes

Tori-Ike is a pair of landlocked marine lakes on Ikema Island connected to the open ocean by an underground tidal channel, creating a unique enclosed ecosystem where entirely different water layers stratify by salinity and dissolved oxygen. The upper marine layer hosts an explosion of jellyfish that pose no danger to divers — their sting capacity has reduced over evolutionary time in the absence of predators — while the deeper hypoxic layer supports unusual anaerobic microbial communities visible as a shimmering chemocline. The protected surface area reflects the surrounding mangroves in mirror-like stillness, producing one of the most surreal diving environments in the western Pacific.