On abandoning his exploration of the Gulf of Carpentaria, Flinders returned to Sydney via the west and south coast of Australia. Although he was determined to complete his work there was no suitable ship available in Sydney.
Flinders boarded Porpoise on 10 August 1803 as a passenger en route to England where he could obtain another vessel.
On 17 August, Porpoise was wrecked on a reef in the Coral Sea (a name bestowed by Flinders). They reached the safety of a sandbank which would be home for seven weeks while Flinders, with 12 others, returned to Sydney in the cutter to secure relief.
A trio of vessels — Rolla, Francis and Cumberland — left Sydney on 20 September bound for Wreck Reef, arriving on 7 October. Some of those stranded on the sandbank would join Rolla which was bound for China; others would go back to Sydney on Francis. A select group of ten volunteers would join Flinders on Cumberland, a vessel of about 11 metres in length, to complete the survey of Torres Strait on the way back to England.
It was a foolhardy mission and Flinders paid a very high price for defying the odds. He knew Cumberland’s deficiencies. He had recorded on 24 September, having only just left Sydney, that she was ‘exceedingly crank’ and ‘very leaky’. He was apprehensive that she would go the full distance around the world. But he persisted in his folly.
By early December 1803, the condition of Cumberland was such that a decision was made to call at the island of Mauritius, then a French possession, 1800 kilometres east of Madagascar in the Indian Ocean. Flinders was hopeful of obtaining a replacement ship there.
Accused of being a spy, he spent six and a half years in detention here. It was the longest period he spent in one place in his adult life.
In August 1805, he received permission to live in the interior of the island. He could reside on the plantation of Louise d’Arifat, provided he did not go more than 10 kilometres from there without Decaen’s permission.
Flinders delighted in exploring the scenic beauty of the area, examining it with a scientist’s eye. Here he learnt French, read, visited neighbours, played tric-trac, attended parties and dances. He learnt to play chess. In many ways, it was a convivial life.
His many friends and activities to some extent alleviated his mind. But still he heard nothing of his release and his absence from Ann was taking its toll. In late 1806, he suffered a period of acute depression. Although he enjoyed the company of his friends, it was nonetheless an alien society in which he could not be totally comfortable.
It was not until March 1810 that, mysteriously, his French captor, the Governor of Mauritius, Decaean, agreed to free Flinders. He was finally released from Mauritius on 13 June 1810 and arrived back in England on 24 October.