The ship had not begun her life as Porpoise at all. She was built in Bilbao, Spain, as the packet Infanta Amelia, and in August 1799 the frigate HMS Argo captured her off the coast of Portugal. The Royal Navy took her into service and sent her to the far side of the world. Commissioned as a storeship for New South Wales, she reached Port Jackson in November 1800 carrying something more hopeful than guns: a cargo of useful European plants assembled by the great botanist Sir Joseph Banks, tended on the long voyage by a gardener named George Suttor, who won free passage for his whole family in exchange for keeping the seedlings alive.

On 10 August 1803 Porpoise sailed from Sydney for India in company with the ship Cato and the East Indiaman Bridgewater. A week out, on the night of 17 August, the little convoy ran up on an uncharted reef roughly 51 miles east of Sandy Cape. Porpoise and Cato struck almost together, beating on sharp coral until they began to break apart. The Bridgewater sailed on into the dark and later reported both ships lost with all hands, then vanished from history herself on a later voyage. But the crews had not died. As the two ships came to pieces, the men and passengers scrambled onto a low sandbank rising barely above the waves, ninety-four souls now marooned on a speck of coral in the open ocean.

They counted their stores and found roughly three months of provisions, but no one knew they were there. Flinders, who had survived a five-year voyage of discovery only to be wrecked on the way home, refused to wait for a rescue that might never come. On 26 August, with the captain of the Cato, he took the largest cutter, christened her Hope, and set out with twelve crewmen for Sydney, some 800 miles to the south. They had an open boat, the stars, and Flinders's incomparable skill with a chart. They reached Port Jackson on 8 September. It was a feat of seamanship that would have crowned any career, performed here almost as an afterthought by a man simply trying to get his people off a sandbank.

Rescue ships sailed at once, and every remaining castaway was brought safely off the reef; in all the disaster, only three lives were lost. The aftermath scattered the survivors across the globe. Flinders pressed on in the schooner Cumberland, only to be imprisoned by the French governor of Mauritius for more than six years, long enough that he died not long after finally reaching home. Others sailed for China aboard the Rolla and, by chance, fought in the Battle of Pulo Aura. Among them was a young officer named John Franklin, in charge of the signals, who would one day lead his own doomed expedition into Arctic ice. The reef holds their wrecks still. Divers rediscovered Porpoise and Cato in 1965, and the site is now protected, a coral graveyard that gave its name to disaster and its survivors to legend.