Barren Island

India's only active volcano breaks the surface about 140 km northeast of Port Blair, and the reef ringing its base is unlike anywhere else in the Andamans — the sand here is black volcanic ash, not white, and old lava flows have set into stepped ledges, arches and walls that drop past 100 m. Reef manta rays are the headline: a group of up to nine works the cleaning stations off the western black sand bay, banking slowly while cleaner wrasse pick them over. Whitetip reef sharks patrol the drop offs, green and hawksbill turtles graze the shallows, and schools of needlefish, barracuda and trevally hang in water that routinely clears to 40 m or more. Sites such as the Washing Machine throw strong down currents, and with the island reachable only by liveaboard this stays firmly advanced ground.