Northern Coral Sea


The Coral Sea Islands Territory includes a most of the islands and reefs in the Coral Sea, to the east of the actual barrier reef.  This is pretty much the same as diving in the open sea, with the outstanding underwater visibility that goes with it. Remoteness ensures pristine reef and large fish that aren’t scared of divers. It’s also hard to beat the adventure of going to spots well off the beaten track. The large expanse of empty ocean off Mackay sees the outer reefs divided in to north western and southern sections, with different corals in each. Unlike the nearby Great Barrier Reef, the reef systems in the Coral Sea are dominated by spectacular sponge ‘gardens’ more so than corals.

The Coral Sea Islands are also bird sanctuaries and centuries of bird droppings led to the larger islands being mined for guano in the 1870s and 1880s. The lack of fresh water meant they were almost never settled. A staff of three or four people run the meteorological station on Willis Island (South Islet), they are the only people living on the islands. The northern islands are split into Osprey Reef and Shark Reef in the north, then the atolls of the Northwestern Group. All are surrounded by very deep waters over 1000 metres deep.

It takes a seven day plus liveaboard itinerary to reach this area, and the only reefs visited frequently are those in the western part of the territory, Osprey, Bougainville, Holmes and Flora and a handful of others. Most of the territory is never visited, except for the occasional private yacht.

Fresh south-easterly (trade) winds prevail between July and December. High seas and swells build up on the southern side of all but the most sheltered reefs. September to January, provides the most reliable weather for Coral Sea access. January and February is cyclone season, and there can be dangerous storms, however the likelihood is also greatest of getting days on end of calm weather as the winds swing around to the north and moderate, the swell and seas drop, and diving conditions improve radically, especially for sites on the southern edge of the reef.

The 24 degree C water temperature during the early spring season (end of August) invites the use of light hoods and gloves while diving. A 3-mm or 5-mm wet suit is recommended. Coral polyps spawn around October or November.


Osprey Rf

Osprey Reef is a sea mount in the Coral Sea some 150 kilometres east of the Great Barrier Reef. All dive sites outside the lagoon have steep drop-offs. Technically, these reefs are not a part of the Great Barrier Reef; they lie from 20-60 miles outside of the reef in the Coral Sea. Of the small number of isolated reefs in the Corals Sea, Osprey Holmes, Bougainville and Flinders Reefs are most often visited. Located out in the open ocean these reefs outstanding visibility, usually over 30 metres and up to 100 metres. The open sea nature of the diving attracts big pelagic fish, especially along the walls. This includes white tip sharks, hammerheads, trevally, tuna, mackerel and barracuda. At Raging Horn, manta rays are frequently seen. The coral and fish life is unbelievably rich and colourful. The terrain offers swim throughs, caves, ledges, coral bommies and trenches.

Liveaboard trips to the Coral Sea usually range from 4-6 days and will often take in Osprey and Ribbon Reefs as a package. Snorkellors are catered for, but it’s adventure diving territory mostly.

Osprey Reef has been an area for active research by James Cook University, encouraged by the tour operators. Depending on what is being funded lately, there are opportunities to see nautilus shells fished up from the depths, or from May to July, to dive with dwarf minke whales.


Osprey Reef – North Horn

Osprey Reef tours offer a shark feeding dive at North Horn, if conditions are suitable. Over the past 20 years, operators have been feeding the resident reef sharks, potato cod and other fish. As a result they will come closer than usual and aggregate around the baits. The crew put fish inside two milk crates and take this down to a particular rock. The crates are secured and everyone lines up around the outside, for the sharks to arrive. This somewhat artificial experience is still pretty exciting, especially if you get an unexpected visit from one of the larger species.

North Horn is the northern most tip of Osprey Reef and is more sheltered from the prevailing SE winds. It offers excellent wall drifts with huge numbers of caves, soft corals and sea fans, clouded over with fish.


Osprey Reef – Admiralty Anchor

The Admiralty Anchor site gets its name from an old anchor sitting in a swimthrough. Flashlight fish can be seen inside a nearby cave. Divers must enter the cave and turn off all lights off. Soon the fish will settle down and start their normal behaviour, which is to aggregate in the cave and signal with a light organ that emits pulses of low level light.

There are huge black coral trees, giant soft corals, big sea fans and red whips along the steep walls. The area is patrolled by schools of giant trevally, dog-tooth tuna, blue spot trevally, barracuda, sharks and bumphead parrotfish.





False Entrance – Osprey Reef

False Entrance oofers resident schooling big eye trevally and barracuda, gorgonian fans, whips and soft corals. In the cooler months you may see cruising hammerheads.






Bougainville Reef


Bougainville Reef lies 140km beyond the eastward of the Great Barrier Reef and 225km east of Cooktown.  It is a small submerged atoll, 2.5 by 4 kilometres with a reef crest that dries at half tide. Like all of the coral sea it offers pristine reef, clear water and huge fish. While it is on the itinerary of many liveaboards out of Cairns, it is rarely visited except in good weather. Although mooring sites are provided in the lagoon, the anchorages are relatively poor and more exposed to the swell than other reefs. There is some limited shelter from the SE trades on the NW corner of the island, but 15-20 knot winds will blow out the site. It can also experience strong currents. It is often dived on the last day of a liveaboard trip, the boat arriving in the morning and leaving at sunset. There is an automatic weather station on the island.

The coral in the area is in exceptional and there are many distinctive communities, Bougainville Reef is considered to be a unique ecological system. The reef is a Maori Wrasse spawning aggregation site and a whale shark aggregation site.

The reefs outer edges are steep walls heading out to water 1000 metres deep. There are relatively fewer easy snorkelling sites. Visibility is excellent and there are plenty of fish, pyramid butterfly fish, unicorn fish, blue dash fusiliers tuna and many others. There are lots of reef sharks, turtles. The reef is packed with hard corals and the reef walls offer large soft corals, gorgonians and other colourful invertebrates. There are also coral overhangs, tunnels and scattered wreckage




The Zoo, Bougainville Reef

5-40 metres

15°30.317S 147°06.890E

This is a dive for encountering big fish, white tip reef sharks, grey reef shark, black cowtail ray, surgeonfish, snappers, sweetlips, drummer, angelfish and leopard blennies. Green and hawksbill turtles are also encountered among the crevices. The coral offers smaller animals including nudibranchs and flatworms.


Wreck of the “Atlas”


Like many isolated reefs in the region, the reef can be very difficult to see in calm weather at high tide with a low sun. Because of shipping mishaps a light has been erected on the reef.  In 1945, the 4810 ton freighter Atlas ran aground and broke up.  The crew was rescued, but the Atlas couldn’t be saved. The wreck of the Atlas stood as a landmark on the reef for many years, gradually breaking up by the stern. The wreck is in the shallows on the reef top and can be difficult to reach. Wreckage is spread down the slope. An area not so noted for coral but there are anemonefish, black-spotted wrasse, red-lined goby, Napoleon Maori wrasse, scissor-tail sergeants, eagle ray and clown triggerfish. Large Potato Cod live in the scattered wreckage.




Wreck of the MV Antonio Tarabocchia



In 1961, the Italian motorship Antonio Tarabocchia (5,851 tons) was travelling in ballast to load sugar in Townsville.  She struck the reef in darkness with squally south-east winds and rain.  Antonio Tarabocchia struck the southern corner of the reef with her bow riding up out of the water.  Two tugs arrived and attempted to haul the freighter off the reef but without success. The wreck of the Atlas stood as a landmark on the reef for many years, gradually breaking up. The wreck is in the shallows on the reef top and can be difficult to reach.




‘Anchors Away’, Bougainville Reef


This is a dive along steep walls covered in hard corals. The crevices in the wall are studded with old Admiralty and more modern CQR pattern anchors, from old wrecks or perhaps salvage attempts on the two steel wrecks. The fish include moray eels, squirrelfish, basslets, goatfish, rock cod, cleaner wrasse and Maori wrasse.


‘Walmart’, Bougainville Reef


This wall has a 700m drop-off. There is a great range of fish life with several types of butterflyfish, humbugs and fairy basslets. Colourful invertebrates including many species of nudibranch can also be found.


‘Corner Shop’, Bougainville Reef


A wall dive with white-tipped and black-tipped Reef Sharks cruising along with large Napoleon Maori wrasse. There are also plenty of clown triggerfish, trevally, wrasse, goatfish, sweetlips, snapper and bannerfish.

Other sites include Crystal Plateau which is noted for big fish including giant potato cod. Dungeons & Dragons is one of the sites on the labyrinth of caves & caverns found along the reef wall. Middle Earth, The Sticks, Between Wrecks are all good drift dives. Deep Six, Dungeons and Dragons, West Point, The Junkyard and Corner Shop are all accessed from moorings and hot boats


Holmes Reef
The Holmes Reef system lies 240km east of Cairns and consists of a complex of three detached lagoons over an area of 17 nm wide by 10 nm.

Like all reefs in the region they can be hard to see, with the exception of the smaller South Reef which has a tall automatic light structure and is dotted with fragments of visible wrecks.

East Holmes Reef is a submerged atoll, about 14 by 10 kilometres. West Holmes Reef is also a submerged atoll and lies 6 kilometres from East Holmes Reef. It is 18km by 7 kilometres with two small cays and a lagoon that is open on the West side. Most of the diving is done around the west and south lagoons.

This is one of the more frequently visited Coral Sea sites, with liveaboards from Cairns doing relatively regular trips here on 4-7 day itineraries. The reef structures at Holmes offer diverse dive sites, 40m plus drop-offs, pinnacles and large car-sized caves. All the dives are patrolled by reef sharks and large schools of pelagic fish. The visibility is usually excellent. It also offers large and colourful sea fans, sponges and sea whips in deeper areas. There is a wide diversity of resident reef fish, turtles, basically everything.





Nonki Bommie – Holmes Reef

16°32.030S 147°48.324E

5-36 metres

This huge main pinnacle is split by a large crack jammed with delicate marine life soft corals and giant yellow and red sponges. Large sea fans can be seen in deeper areas. The spilt is large enough to swim though in spots and the pinnacle is covered in swirls of pelagic fish including sharks and tuna. Schools of bigeye trevally are at the base and the top of the pinnacle. Table coral and small brain corals provide shelter for a range of smaller fish including hawkfish, parrotfish, rabbitfish, pyramid butterflyfish and juvenile golden snappers, fairy basslets and damselfish. Small nudibranchs can also be found.  Sand is reached at 20 metres, divers can descend down a reef slope to as deep as 40m before it drops over a wall into 300 metres.


Amazing Caves


This site offers caves along a reef wall.  One large cavern, with 2 entrances at 9 and 16 metres, exits on the other side of the formation into a gutter at about 6 metres. Reef sharks are resting in the caves and gutters and there are lots of smaller cryptic fish and invertebrates in the caves. Some caves are a tight squeeze and the silty sand can get stirred up. As with many dives in the area along the reef wall it is possible to descend into great depths if unwary.

Looking from the sandy slope out to the blue turn left and the reef wall ascends up from the deep where there are caves. The reef here starts about 3 metres from the surface, drops to about 16-20 metres and then slopes diagonally to 40 metres where it drops off to the unknown.   Here you might surprise a few white tip reef sharks laying in wait, when exiting the caves explore the vast array of gutters and swim throughs.


Golden Wall


This sheer wall dive offers lots of sea whips, gorgonia, black coral trees and colourful soft corals. It is usually jammed with schools of pelagic fish as well as sharks and turtles.


Predators Playground


This is the main shark feeding area for this reef and it is a dive always popular with visitors. This time a floating shark cage is used. After the feed, there are also small bommies nearby with plenty of pelagic fish.


Turtle Graveyard


This overnight mooring site is used for night diving offering a wall with numerous caves. Is area is also visited during the day as a drift dive. For a more leisurely dive, there is a flat sandy large area at 10 metres where there are lots of small bommies and swim throughs.

The Cathedral/Abyss

This is a dive in the lagoon on a large coral formation near a break in the reef. Divers after a deeper dive can descend down a crevice that can have down currents on a falling tide. This leads to the wall dive known as the Abyss, but this is better done separately as a planned drift dive. This 1000 metre drop off offers caves, gutters and canyons.  There are lots of small reef sharks and plenty of pelagic fish.


Line of Sight

This is a drift dive along a ridge between the two reefs. There is lots to see but the current is sometimes strong and it can have poorer visibility than other sites.


Northern Lights

At the northern end of East Holmes Reef offering very large pinnacles and gutters. There can be a lot of current at the site and it needs to be well planned as a drift dive for experienced divers.




This site in the West Holmes lagoon offers a spectacular array of big pelagic fish that crowd around this prominent pinnacle when the tidies running.


Leopard’s Lair

This is one of the East Holmes reef sites and offers a nice pinnacle dive noted for the large numbers of leopard sharks resting on the bottom. The rest of the pinnacle also offers good coral and interesting smaller marine life.


Willis Islets / South Islet

8m in lagoon


Willis Islets

Willis Island is noteable mainly because it is the only inhabited island in the Coral Sea. For that reason it tends to be a popular stopping point for cruising yachts. It is also strangely visited by cruise ships, that pass by and sometimes anchor. The journey to Willis gives a reason to travel into International Waters where the duty free stores can lawfully be open for business.

The Willis Island weather monitoring station was established in 1921 in order to provide a cyclone early warning service for Queensland. It houses 4 staff for 6 months at a time. They can be friendly and accommodating, and eager to show visitors around. The station has a recreation room which includes amenities such as a pool table, darts and table tennis.

The reef is a sunken atoll, bank 45 by 19 km with 3 islets on the Northwestern side: North Cay, Mid Islet and South Islet or Willis Island. Willis Island is 10 m above high tide. The islets are important nesting areas for birds and turtles. There is no port or harbour at Willis, only an offshore anchorage that provides poor shelter. The islet has 3 or 4 coconut trees and lush vegetation, although all the standing vegetation was stripped off by Cyclone Yasi in 2011, which also changed the shape of the cay due to massive waves. The reefs are slowly recovering.

The most common inhabitants are seabirds that are very numerous and noisy.





Lihou Reef

Lihou Reef and Cays is the largest atoll in the Coral Sea.  Lihou Reef has a lagoon of 100 by 30 kilometres. Lihou is a ‘U’-shaped series of reefs facing west-southwest, connected by shallow, narrow passages. Most are unsafe to enter. The reef has 18 small and low islets. Grasses and small herb-like plants grow on five of the cays. Lihou Reef was declared a Nature Reserve on 16 August 1982 as a part of theLihou Reef National Nature Reserve. The lagoon is up to 60 metres deep, although it is shallow close to the cays. The cays offer submerged coral heads in 12 m or less.

The undisturbed sandy habitat of the islets is used for nesting by green and hawksbill turtles. The forest and shrubland of the cays support breeding populations of terns, boobies, tropicbirds and other seabirds. The coral reef has a distinct community of marine flora and fauna. Marine seaweed beds are a particularly noted feature, frequently covering a greater area than the corals. A large number of shipwrecks are also present on the reefs and the modern main freighter shipping channel passes just to the east of the reef.

Recreational diving is limited to the ten commercial tours of up to 30 passengers each permitted per year, of which it is doubtful that many use the reef, and small numbers who arrive by private yacht.







Coringa-Herald National Nature Reserve

Magdelaine Cays, Coringa Islets and Herald Cays are part of the 8856 km2 Coringa-Herald National Nature Reserve, created on 16 August 1982. The 6 islets of the nature reserve are small, it’s mostly reef and open ocean. This area supports high biodiversity, about 745 species of molluscs, 400 species of fish and thousands of seabirds. Female green turtles also come ashore, usually between November and April to lay eggs on the cays.


Mellish Reef, Heralds Beacon Islet

12m lagoon



Mellish Reef lies about 300 km to the east of other islands in the Northwestern Group and is the most distant reefs from the Australian continent, 580 nm east from Cairns. It has the outline of a boomerang around 10 km in length and 3 km across. The reefs enclosing the narrow lagoon, are completely submerged at high tide. Near the centre of the lagoon is the only dry land of the reef, the vegetated Heralds Beacon Islet. The island is a small cay measuring 600 m by 120 m and only a few metres high. The anchorage is good for NW thru SW winds, but it is exposed to the winter swell from the Tasman Sea at high tide. The area has clouds of thousands of seabirds, brown boobies, white masked boobies, common noddies and sooty terns. The small Northeast Cay is encircled by a reef of 3 by 3 km, while Southwest Cay (4 km Southwest of Northeast Cay), is enclosed by a reef of 2 by 2 km)


Magdelaine Cays

Magdelaine Cays is one large atoll structure, almost 90 by 30 km. The reserve contains six islets and cays ranging in size from 16 to 37 hectares and covering a total area of 124 hectares. South-East Magdelaine Cay is the largest of these. The islets are made up of coral sand, rocks and coral rubble and are no more than about five metres above sea-level. North-East Herald Cay and parts of South-East Magdelaine Cay have thick forests of Pisonia and Cordia trees. Grasses and low shrubs grow on the other islets apart from North-West Magdelaine Islet which has no vegetation and offers a relatively poor anchorage.





East Diamond Islet, Tregosse Reef

Anchorage, 17°26.411’ S – 151°04.220’ E
Thislarge, partially sunken atoll is 100 by 52 km with 4 islets and 2 small submerged reefs in the Northeast and Southeast: West Diamond Islet, Central Diamond Islet, East Diamond Islet on the Northeastern rim of the former atoll, and South Diamond Islet, East Tregosse Reef and West Tregosse Reef on the Southern rim

East Diamond Islet has a good anchorage in a shallow bay with brilliant white sand with nearby coral heads. The islet supports clouds of seabirds including lesser frigatebirds, a thousand pairs of red-footed Boobies and large numbers of noddies, boobies and terns. The islet is marked by a beacon.




Flora Reef

This relatively small submerged atoll is 5km by 4 km. It is a horseshoe shaped reef with no islets. The bottom drops away quickly outside the lagoon and is affected by currents.


The diving is noted for some strange caves in the coral with a shape that look like lava tubes. The walls are popular dive spots with the few visitors and offer plenty of silver tips and grey reef sharks.The usually excellent visibility can be reduced by strong northerlies.


Flinders Reefs


Located 200 kms east of Townsville, Flinders Reefs (North and South), Herald’s Surprise and Dart Reef form a cluster of reefs over a 66km by 26  in area. North Flinders Reef is the largest atoll and dominated the area. It has 2 islets, with Flinders Cay a 200 m long cay with a height of 3 metres. This reef is relatively close to the mainland and is often on 7 day live aboard itineraries.

The Flinders Reef complex offers walls, swim-through canyons and coral gardens. It is known for regularly dived sites such as Anemone City, Berlin Wall, Trigger Happy and the Cod Wall. Currents are generally light in most areas.


Soft Spot

This area offers hundreds of colourful soft coral trees growing on coral pinnacles. As with all sites, fish and invertebrate life is excellent.


Anemone City

Purplish football anemones are common throughout the Flinders Reef complex, with their clownfish in attendance. This site in the centre of the lagoon and consists of 5 large coral pinnacles covered in fish, coral and anemones. There are a few crevices in the pinnacles, one covered in pink hydroids.


Watanabe bommie


This deep pinnacle on the western side of the reef is clustered with schools of pelagic fish. Sharks patrol the huge office block-sized pinnacle and it is covered in soft corals, gorgonian and sea whips.


Rock Arch

This is a wall dive on the SW side of Flinders Reef offering coral formations that are interconnected to form caves and crevices packed with colourful invertebrates.


China Wall, Boomerang Reef

Just to the south of the Flinders Reef lagoon, the small Boomerang Reef is also often visited and has some well-known dive sites. The reef is known for its wall dives, with the reef edge dropping in to 1000 metres. The walls are patrolled by sharks and pelagic fish, while the reef is covered in sea whips, gorgonia and black coral trees. At depth, gorgonian sea fans can grow to a width of 4.5m on the reef walls of the region. Whaler Station and Cod Wall are other well-publicised sites although there are many similar sites in the area.


Scuba Zoo, Boomerang Reef


This is a shark feeding site with up to 30 or more sharks that come to put on a show. Divers once sat on the sand to watch the rather timid reef sharks circling for some time before they make for the baits. These days there are 4 large shark cages permanently on a sandy bottom as a refuge. Most divers just sit on the cages. When the bait box is then opened the sharks rush in and it’s all over in a minute.


Marion Reef


This large circular atoll is remote. It is over 400 kms from the mainland coast, and lies at the extreme southern end of the north western outer reefs. It is also well separated from the nearest reefs to the north. Biologically it is also separated from the larger Coral Sea Plateau to the north by the Townsville Trough, and it sits on its own plateau. The lagoon is over 30 km in diameter and offers a good anchorage. The atoll is composed of three main reefs on the eastern side: Marion, Long and Wansfell; and a number of smaller reefs on the west. Three small sand cays are located on the eastern side of Marion Reef: Paget Cay, on Long Reef, Carola Cay and Brodie Cay. The lagoon is studded with coral pinnacles offering good diving. The deeper pinnacles offer the better hard coral formations. The pinnacles are patrolled by fish and small sharks will approach divers. There are plenty of sea snakes. There are also great wall dives outside the lagoon with excellent soft and hard corals, gorgonia, sea whips and other invertebrates. The walls are patrolled by plenty of school fish.