Manuk

Manuk is a day's sail from anywhere, an active volcanic cone whited over by seabird colonies, and it hosts one of the strangest wildlife encounters in diving: sea snakes in extraordinary numbers, surfacing to breathe, hunting through the boulders, and investigating divers with frank, harmless curiosity. Several may attend a single diver at once, tongue-flicking masks and fins before losing interest. The snakes headline, but the volcano's slopes also carry schooling fish in bulk, dogtooth tuna, and seasonal traffic of scalloped hammerheads off the deeper terraces. Warm venting sand in the shallows reminds visitors what the mountain is. The etiquette is simple and absolute: let the snakes conduct the meeting, and never handle or corner one.

The moment you come for: Dense, curious sea snakes; an active volcano in open sea; hammerhead odds off the terraces.

Topography: Volcanic slopes and boulder reef around an uninhabited, bird-covered volcano far out in the Banda Sea.

Current: An isolated volcano in open sea; conditions range from benign to sporty with no shelter alternatives nearby.

Hazards: Venomous snakes that must not be touched, open-ocean exposure, and extreme distance from medical help.

Conservation: The island is an important seabird rookery and the snakes are protected by remoteness; no landings, no handling, nothing left behind.

Nitrox: Worth it here — profiles sit in the range where enriched air meaningfully extends no-stop time (with the training to use it).