The Capricorn and Bunker Cays form part of a distinct geomorphic province at the southern end of the Great Barrier Reef.

The sea level was much lower during the last ice age (at the end of the Pleistocene period) and the coastal plain on which today's reefs and cays developed was completely exposed.

One Tree Island is a Shingle cay and part of a Lagoonal Platform Reef:[4] In 1803 Captain Eber Bunker of the whaling ship Albion was the first European to discover the region and gave his name to the southern group.

[5] The Albion was 362 tons and registered in London,[6] the ship was fitted with 10 guns, and a crew of 26; she was built in Deptfordand, Britain ownered by, Messrs. Champion; and used for general cargo[7] The southern cays and reefs were first charted between 1819 and 1821 by Lieutenant Phillip Parker King RN initially in the Mermaid and later in the Bathurst.

The main charting exercise for all the islands and reefs was carried out in 1843 under the command of Captain Francis Blackwood in HMS Fly which was accompanied by the Bramble.

The naturalist, Professor J. Beete Jukes, was on board the Fly and his published journal provides valuable information on some of the cays.

[9] Researchers there focus on topics such as climate change and coral bleaching, eutrophication of reef ecosystems, carbonate chemistry, geology, sedimentation, birds, and ecological sustainability.

Captain Norris, who went down in charge of the boat, unbent the sails, so that the position of the vessel might as much as possible remain unaltered; he left the yards and masts standing.

[15] and 6 months later it was reported as The Rose, schooner, has returned from the wreck of the Jane Lockhart, on Masthead Reef, whither she went on 15 June Captain Dwyer informs us that the Jane Lockhart still lies in a very snug position, and he has no doubt but that himself, and Mr Norris, the purchaser of the wreck, will be able, ultimately, to raise the vessel and bring her safely to Rockhampton Nearly the whole of the period that they were at the reef, very heavy weather prevailed, staving operations towards the recovery of the cargo, but luckily the strong SE winds lulled for about three days Captain Dwyer availed himself of the occasion, set to work, rigged up a staging between the masts of the Lockhart, schooner, and by means of a rope and a South Sea Island diver, managed to bring up from eighty to ninety large iron pulley wheels, besides a quantity of machinery and sundries, comprising Ale, porter, liqueur brandy, cutlery, ironmongery, etc.