The Abyss is Holmes Reef's big wall drift, and Dive the World calls it among the most popular dive sites at Holmes. It describes a steep wall dropping more than a kilometre, dived as a drift, with grey reef and whitetip reef sharks, mackerel, sweetlips, nudibranchs and giant clams. Marinelife.org.au lists it as 'The Cathedral/Abyss', a large coral formation on a 1,000 m drop-off with caves, gutters and canyons, small reef sharks and pelagic fish, and warns of a crevice where down-currents can occur on a falling tide. Dive the World lists Cathedral as a separate wall site, so the two are now separate rows.

The topography is dramatic. The reef edge is broken by caves, gutters and canyons that cut into the wall, and beyond them the face drops into the deep. Drifting along it, divers pass from one feature to the next, peering into caves and gutters while sharks and pelagics move along the edge.

The current that makes it a drift also brings in food, and the wall is well covered in hard and soft corals, fans and sponges. Grey reef and whitetip sharks are regular, mackerel and other pelagics pass, and sweetlips shelter in the gutters. Giant clams sit on the upper reef, and nudibranchs are common on the wall.

The Abyss suits experienced divers comfortable in current and on a bottomless wall. The down-current warning should be taken seriously: stay away from the crevice on a falling tide and keep a close eye on depth. It is also shown on Mike Ball's itinerary map.

Liveaboard only. Mike Ball's Spoilsport includes Holmes Reef on its 7-night Coral Sea exploratory (Cairns return), the 7-night Yongala & Coral Sea expedition (Townsville to Cairns) and the 10-night Coral Sea Odyssey; the overnight crossing from Cairns is about 240 km of open ocean. Holmes is normally allocated a day on these itineraries.

The Abyss is usually run as a drift from a tender; it is also shown on Mike Ball's itinerary map.

Holmes Reef is a pair of isolated Coral Sea atolls about 240–250 km east of Cairns with no land for shelter. Dive the World calls it a fair-weather destination: SE trades over about 20 knots (common June–August) make the crossing and surface conditions rough, although the lagoons and western sides offer some protection. Currents are normally gentle but can be strong in the channels and on the ridges, especially on a falling tide.

September–December usually has the calmest seas and 20–40 m visibility; December–April is cyclone season.

Drop from the tender up-current, descend to 20–25 m along the wall and drift past the caves, gutters and canyons. Avoid the crevice where down-currents are reported on a falling tide. Ascend along the wall with an SMB for pick-up.

Coral Sea liveaboards visiting Holmes Reef (Mike Ball Dive Expeditions) – occasional.