Trim was born in 1799 aboard the ship, black with white paws, chin and chest. Trim would not have been the only cat on board Investigator; most ships kept a few cats onboard to catch rats and mice that could cause havoc by eating supplies or gnawing on ropes.

But Trim's personality appears to have been bigger than the other ship cats.  Flinders wrote, in A Biographical Tribute to the Memory of Trim.

'The signs of superior intelligence which marked his infancy procured for him an education beyond what is usually bestowed upon the individuals of his tribe,'

 'And being brought up amongst sailors, his manners acquired a peculiarity of cast which rendered them as different from those of other cats.'

As a kitten, Trim fell more than once into the ocean but paddled back to safety and climbed onto the ship.

'He learned to swim and to have no dread of the water; and when a rope was thrown over to him, he took hold of it like a man, and ran up it like a cat,' wrote Flinders.
'In a short time, he was able to mount up the gangway steps quicker than his master, or even than the first lieutenant.'

Noting his strong survival instinct and intelligence, Flinders and the crew made him their favourite. He was named after the butler Corporal Trim in Laurence Sterne's novel ‘Tristram Shandy’ because Flinders considered him to be a faithful and affectionate friend. Flinders even wrote a biography for his constant cat companion as well as other tributes and poems.

Trim sailed with Flinders on HMS Investigator on his voyage of circumnavigation around the Australian mainland. Trim also managed to survive the shipwreck of HMS Porpoise on the Great Barrier Reef, in 1803, using another of his 9 lives! When they ran aground and the crew, including Trim, had to swim to safety on a small island.

Trim was said to have helped keep the stranded men's spirits up while they waited seven weeks for rescue.

When Flinders was accused of spying and imprisoned under house arrest by the French in Mauritius on his return voyage, a faithful Trim shared his captivity. During his imprisonment, Flinders wrote a biographical tribute to Trim in which he described him as "one of the finest animals I ever saw... [his] robe was a clear jet black, with the exception of his four feet, which seemed to have been dipped in snow and his under lip, which rivalled them in whiteness. He had also a white star on his breast."

Trim stayed with Flinders the whole time — but he was allowed to wander the island.
During one of his outdoor explorations in 1804, the cat failed to return, much to the distress of Flinders.
Although never proven, a heartbroken Flinders attributed his disappearance to his having been stolen and eaten by a hungry slave. Flinders wrote about the demise of his friend:

"Thus perished my faithful intelligent Trim! The sporting, affectionate and useful companion of my voyages during four years.
"Never, my Trim, 'to take thee all in all, shall I see thy like again', but never wilt thou cease to be regretted by all who had the pleasure of knowing thee.
"And for thy affectionate master and friend, he promises thee, if ever he shall have the happiness to enjoy repose in his native country, under a thatched cottage surrounded by half an acre of land, to erect in the most retired corner a monument to perpetuate thy memory and record thy uncommon merits.

Flinders never got a chance to erect a monument to Trim, but a number of statues now stand as memorials to the adventurous cat — in England and in Australia — and his story lives on.