A chart showing the location of Great Detached Reef (bottom right) and Thursday Island (top left)	Great Detached Reef - Southern Entrance is located at the bottom of GDR and is obvious

Great Detached Reef is a reversed C shaped reef made up of a number of separate sections. It is located a little off what is the main outside section of the Great Barrier Reef, although here that reef is merely a series of small bommies or reefs. Great Detached Reef is 11.5 nm from north to south and 8.8 nm east to west. The west (open) side of the reef has a series of bommies and small reefs along a large part of its length.

There are only a couple of boats that travel to this area, one being Kalinda which routinely does full boat charters there in November and December. Another boat does some trips there and one more might go there once or twice a year.

Kelly and I travelled here in November 2016 on Kalinda with fellow members of St George Scuba Club when we chartered the whole boat. We flew into Horn Island (next to Thursday) and started our trip from there.

There are two entrances to the Great Detached Reef lagoon (not counting the open western side). Southern Entrance is located between the southernmost section of reef and the section that runs from here north. The dive site is located on the southern side of the entrance and outside the lagoon. Its location is GPS S11º 48' 55.3" E144º 00' 57.4". The depth on the top of the reef is five metres and from here it drops steeply to 200 metres.

A typical section of reef	Another photo of the reef

We anchored in about 25 metres and we dropped to the anchor and then headed south along the reef and wall. We dropped to 30 metres which has the best section of wall and gorgonias. After five minutes we gradually started a very slow ascent up the wall and then the slope. There are thousands of gorgonias on this dive, ranging from huge to small in size.

As we go along we see lots of sharks, grey reef, white-tipped reef and black-tipped reef sharks. The reef has lots of vertical gullies that run from near the top of the reef down deeper. In these gullies and elsewhere there are lots of titan triggerfish and their nests. Luckily it they have not yet laid their eggs, so the triggerfish are not aggressive. I would hate to be here when the eggs are being guarded.

Kelly with one of the large gorgonias	Kelly looks at an orangefin anemonefish from the anemone at left

As well as the sharks and triggerfish, we see quite a few barracuda, kingfish, plenty of giant trevally as well as other species of trevally. We also see plenty of Moorish idols, long-finned bannerfish and butterflyfish. There are also a lot of parrotfish and two firefish.

We also see a few nudibranchs and slugs, as well as some tiny yellow "bugs". They are obviously some sort of crustacean, but who knows what.

Inornate chelidonura	A whole lot of some sort of "bug"

We come back a bit shallower and gradually ascend again to 10 metres where we spend 15 minutes before ending the dive with more than 15 minutes around the five metre level.

We dived here in November, the water temperature was about 28ºC, visibility about 20 metres. A really good dive site.