Mariner's Cave

Mariner's Cave is a partly submerged sea cave in the Vava'u island group of Tonga, accessible by swimming through an underwater entrance into an air-filled chamber inside the limestone cliff. It is reached by boat from the islands around Vava'u, with the entrance found along a rocky coastline rather than from shore. The cave is best known for the effect of ocean swell compressing air inside the chamber, causing a fog to form as divers surface inside it. Because entry requires ducking underwater through a submerged opening timed with the swell, it is generally treated as a site requiring guidance and calm conditions rather than something to attempt independently.

Confirmed by our research team, reported by independent divers, or observed nearby via iNaturalist — each entry is labelled with its source.

• Princess DamselPomacentrus vaiuliReported here · unconfirmed
• Lined BristletoothCtenochaetus striatusReported here · unconfirmed
• Indian Bullethead ParrotfishChlorurus sordidusReported here · unconfirmed
• Coral DamselfishPomacentrus maafuReported here · unconfirmed
• Yellowbar ParrotfishScarus schlegeliReported here · unconfirmed
• Brown TangZebrasoma scopasReported here · unconfirmed
• Manybar GoatfishParupeneus multifasciatusReported here · unconfirmed
• Humbug DascyllusDascyllus aruanusReported here · unconfirmed
• Dusky SurgeonfishAcanthurus nigrofuscusReported here · unconfirmed