The discovery of the Great Barrier Reef (then, of course, unnamed) to the modern world was made by Captain James Cook in the year 1770, during his voyage to the southern hemisphere.
His ship was HM Bark Endeavour and he went armed with a team of top scientists.
Primarily a mission to make astronomical observations of the planet Venus, the voyage was also one to discover and claim new lands for the British flag.
Previous to Cook's arrival, the Reef had been known only to the local tribes people of the area, the Aborigines.
At that time, there were around 40 separate Aborigine tribes living up and down the Reef coastline, surviving off the rich food sources of the area.
[In the mid 1600s however, over a century before Cook's voyage, the Dutch explorer Able Tasman had navigated the western coast of a large unknown landmass which had been recently discovered by fellow countryman Van Diemen.
Tasman also explored a large island off the south-eastern corner of this landmass - Van Diemen's Land, named after the Dutch discoverer (that island is now Tasmania).
Van Diemen's original voyage had been inspired by the Greek philosopher Aristotle, who had concluded that a large landmass - terra australis incognita, or the 'unknown southern land' - must exist because of the earth's assumed natural symmetry.
The map above is an early (1618) Dutch map of terra australis incognita. Click to view larger.]
Despite Van Diemen and Abel Tasman sailing through these southern waters, no westerner had yet discovered the eastern coast of the continent that was later to be named Australia.
Cook's route around New Zealand and eastern Australia, during his 1768 - 71 voyage
By the end of April 1770, with his astronomical studies complete, James Cook had successfully circumnavigated and claimed New Zealand and was heading westwards towards the Dutch-discovered land.
At daybreak on April 19th, he and his crew saw a new horizon of a low-lying land mass, and logged the sighting as the first glimpse of what he assumed to be Van Diemen's land.
But due to a strong gale blowing from the south, Cook was forced northwards and so wasn't able to reach the point of land that had first caught their attention.
On the 29th, the Endeavour and her crew dropped anchor in a sheltered bay.
Though not welcomed by the native tribes people, the head naturalist among the crew, Sir Joseph Banks, began collecting and analysing plant samples. The huge variety of plants collected by Banks led Cook to name the place Botany Bay.
Further up the coast, Cook made another stop on May 6th in a larger bay which he named Port Jackson, later to become Sydney Harbour.
Continuing northwards hugging the coastline, HM Bark Endeavour sailed towards the warmer tropical waters and the southern end of an unknown huge coral reef system.
Several weeks later, on Whit Sunday, June 3rd, Endeavour sailed through an impressive group of mountain islands. The slopes came down to white sandy beaches and clear, calm turquoise waters - a far cry from the dark, rough waters of the south.
Cook, ever creative, named these waters the Whitsunday's Passage.
Although Captain Cook was constantly monitoring the fluctuating sea depths, he was in relatively safe waters and very unaware of the complex reef system further out from the mainland.
As he pushed northwards, all the time charting the unknown waters, the reef system became more complex and - more importantly - started appearing much closer to the mainland shore.
The rude discovery of the Great Barrier Reef came at a few minutes before 11pm, on June 11th, when HM Endeavour stopped dead in her tracks after striking the south-eastern tip of a coral reef, holing her bow.
With each crew member to hand, every effort was made to refloat the damaged ship. Working through the night, all unnecessary objects were thrown overboard, including the ships guns and ballast, in an effort to lighten the ship's weight.
After nearly 24 hours aground, Endeavour finally refloated at 10.20pm the following night.
After the horrifying ordeal and makeshift repairs, Cook limped his ship to land as quickly as safely possible, beaching at a small harbour and river mouth which he later named Endeavour River.
The ship, Cook and the crew remained here for several weeks while the ship's carpenters and blacksmiths did all that was necessary to make Endeavour seaworthy.
Encounters with the Aborigines happened on a daily basis. Although frightened to start with, the natives soon became accustomed to Cook's presence and contact began on a very basic level.
By mid July, Endeavour was about ready to sail, but unfavourable weather conditions kept her confined to the river mouth for another couple of weeks. On August 6th, Cook finally sailed Endeavour out into the waters of the Reef.
Armed with a new knowledge of the presence and danger of so many coral reef systems in such close proximity, Cook had a lookout placed atop the highest mast of Endeavour.
Five days after setting sail, Endeavour dropped anchor offshore an island with a distinct mountain peak - Lizard Island, so named by Cook because lizards were the only animals that he saw here.
Cook climbed to the summit, some 1178 feet above sea level, and could for himself get a proper look at the waters in which he had been trapped for so long.
His initial shock of seeing so many reefs together was soon replaced with relief when he looked eastwards and saw large waves breaking followed by deep blue open sea - the edge of the Great Barrier Reef, and Cook's gateway to safe sailing.
The discovery of the Great Barrier Reef was made by accident, but Cook returned to the southern hemisphere in 1772 with a new ship and crew - this time to purposely determine the existence and geography of the new found lands that had once been thought of as imaginary.
[All images here have been verified as being available for reproduction in public domain.]
References for information: National Library of Australia