Season, conditions and how long to allow, with the number of species this index holds a record for at each one. They are grouped by region because that is what actually separates them: a Coral Triangle muck site and a Caribbean wall have almost no species in common and are not the same activity.
More reef fish and more coral species than anywhere else on earth, and the birthplace of muck diving: volcanic sand and silt in sheltered straits, dived slowly and close to the bottom for animals a few centimetres long. Warm all year, rarely clear, and the reason most of this index exists.
A narrow channel of black volcanic sand between mainland Sulawesi and Lembeh island. Sheltered water, short boat rides and a high density of cryptic species.
Nudibranch diversity, and the most photographed muck sites in the Philippines. Two to three hours by road from Manila.
Harbour muck, psychedelic frogfish, and rhinopias in season. Shallow and rarely crowded.
Shore-entry muck twenty minutes from the airport. Apo Island is a separate day trip.
Black sand on four coasts, from the Tulamben shore dives to Secret Bay in the far west. The muck is spread across the island, not gathered in one bay.
Milne Bay, Tufi, Kimbe Bay, Rabaul and Kavieng. Black sand in sheltered bays, wartime wrecks, and reefs that are among the healthiest in the region.
Four kinds of diving in one country and almost no overlap between them: the Great Barrier Reef and the Coral Sea in the tropics, Ningaloo and its aggregations in the west, kelp and seadragons in 12 to 20 degree water in the south, and jetty muck on both coasts. A trip here does one of them.
Clear warm water and current-driven diving, on atolls in one case and on a narrow enclosed sea in the other. The Red Sea is the outlier on this site: it has been isolated long enough that a high proportion of its fish occur there and nowhere else.
Atoll diving in current. Grey reef sharks at the channel mouths, manta at cleaning stations, and whale sharks along the outer reef in the south.
Warm, clear and reef-dominated, with wrecks in the north and offshore reefs in the south. Roughly one reef fish in seven is found nowhere else.
Cold upwelling on the equator, and a fauna cut off from the Indo-Pacific by five thousand kilometres of open ocean, so almost nothing here is on the other lists. Current-driven, often cold, frequently not clear, and dived for large animals rather than for coral.
Cold upwelling on the equator. Hammerhead schools at the northern islands, sea lions and the red-lipped batfish in the south. Current-driven and demanding.
Liveaboard only, 550 km offshore. Hammerhead schools at fixed cleaning stations, and the white-tip reef shark night dive.
Four volcanic islands 400 km out in the open Pacific, dived from liveaboards out of Los Cabos. Bare rock, seamounts and vertical walls, with almost no coral reef.
A separate ocean with a separate species list: no anemonefish, no Indo-Pacific lionfish except the introduced one, and its own angelfish, groupers and gobies. Clear water over carbonate banks, walls that start shallow, and one of the best macro sites in the region under a road bridge in Florida.
Coral reef in the Keys, drift diving and large sharks off Palm Beach, and Blue Heron Bridge, which is muck diving in a tidal channel and one of the best macro sites in the western Atlantic.
Clear water over a shallow carbonate bank, walls that drop into deep ocean, and the most reliable shark diving in the western Atlantic. Also blue holes, and dolphins in open water on the banks.
Three small islands with steep walls close to shore, easy shore diving and consistently clear water. Bloody Bay Wall on Little Cayman is the best-known wall in the Caribbean.
Species counts are of entries in this index with a record at that destination, not of everything that lives there. Ratings, depths and habitats are per destination, because the same animal is a different proposition in different places. Where a destination has no named sites yet, the diving is described on its own page and the site list follows.