She made five voyages for the British East India Company (EIC), the last one transporting convicts to Port Jackson as one of the vessels of the notorious Second Fleet.

Homeward bound, she reached Cochin on 7 April 1785, and St Helena on 5 July, before arriving at The Downs on 5 September.

Homeward bound, she crossed the Second Bar on 25 December, reached St Helena on 28 April 1787, and arrived at The Downs on 5 July.

Homeward bound, she crossed the Second Bar on 20 December, reached St Helena on 6 May 1789, and arrived at The Downs on 12 July.

[2] Captain Thomas Gilbert started the voyage on 17 November 1789, bound for Botany Bay and China.

[1] In company with Surprize and Scarborough, Neptune finally sailed from England with about 502 convicts (424 male and 78 female)[3] on 19 January 1790.

At some point on the voyage Gilbert died and his replacement as master was Donald Trail;[1] the surgeon was William Gray.

She arrived at the Cape of Good Hope on 13 April 1790, and spent sixteen days there, taking on provisions, and twelve male convicts from HMS Guardian, which had been wrecked after striking an iceberg.

During the voyage 147 male and 11 female convicts died, for a total death rate of 31%;[4] 269 (53%) were sick when landed.

After a trial lasting three hours before Sir James Marriott in the Admiralty Court, the jury acquitted both men on all charges "without troubling the Judge to sum up the evidence".

He apparently fathered a child by his convict mistress, Catherine Crowley, conceived early on the voyage.