A chart showing the location of Great Detached Reef (bottom right) and Thursday Island (top left)	Great Detached Reef - Captain Bloods Wall of Terror is the whole section on the southermost part of the reef

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.

Captain Bloods Wall of Terror (no idea where the name comes from) is located on the southern side of the Great Detached Reef lagoon. This side is a reef that runs from west to east before turning north. Its location is GPS S11º 50' 35.2" E144º 02' 53.5". The depth on the top of the reef is about five metres and from here it slopes drops gradually to 25 metres before dropping steeply to 300 metres.

This dive is always done as a drift dive as it is far too deep for any boat to anchor. The whole section of the southernmost part of the Great Detached Reef can be considered the one dive site, where you start your dive will depend on the direction of the current and if you have dived here before (and hence want to see more of the reef). We did two dives here, both in the same direction but starting in different spots.

A grey reef shark	Another grey reef shark

The actual current once in the water may be different to the surface current, so a lot of flexibility needs to be involved. The way we did it, the Kalinda came in close to the reef and half the divers jumped in the water in quick succession. It then moved away while we swam closer to the reef. We then descended and once the current was ascertained, we drifted in that direction. For the first dive there was only a very slight current, we could have swum against it easily if needed. The second dive we had a nice current, easy to go against, but enough to push you along without swimming.

The attaction of this dive is sharks and extremely steep walls. Once you are down on the reef, you will see that the vertical section of the wall has large numbers of very big gorgonias and sea whips. These can be quite spectacular and will make great photographs. We dropped to about 28 metres and mostly kept at this level, although I dropped a couple of times to 33 metres to take photos of gorgonias.

As we drifted along, we saw plenty of sharks, mostly grey reef and white-tipped reef sharks. We also saw at least one silver-tipped reef shark. We saw about 30 sharks all up on our two dives. This dive also has clown-trigger fish, my favourite tropical fish of all time. They are so beautiful. We saw three on one dive and two on the other.

We did not see that many starfish out here	One of the clown tiggerfish we saw

There were also plenty of rainbow runners, red bass, parrotfish, unicornfish and surgeonfish. We also saw some eels, a few nice nudibranchs and all the normal tropical species. We gradually ascended up the wall and then the slope as we went along. You cannot really go into the shallows to do a safety stop as it would be too far to swim back to the boat once you needed to surface. We did about 37 minutes on each dive on the bottom before ascending from 12 metres to do our safety stop at five metres. Here we sent up a safety sausage so the boat would know where we were.

Once we finished the safety stop, we swam out away from the reef as we ascended and then out a little bit more. The Kalinda came in close to us and we all quickly exited the water. All very military like!

We dived here in November, the water temperature was about 28ºC, visibility about 30 metres. A brilliant dive site.