[2][3] The family lived in Saffron Hill, London, until 1765 when they moved to Devon after his father as a lieutenant colonel was made commandant of the Plymouth division of marines.

In February 1781, Collins was posted as captain for a detachment of marines aboard the 74-gun HMS Courageux in the Channel Squadron commanded by Admiral Richard Howe, where he took part in the relief of Gibraltar.

[2][12] In October 1786, after three years on half-pay stationed at Chatham, Collins volunteered for service in the proposed penal colony of New South Wales.

He sailed from England in April aboard HMS Calcutta, arriving at Port Phillip in October to found a penal colony.

After landing at Sullivan Bay near present-day Sorrento, he sent First Lieutenant James Hingston Tuckey of the Calcutta to explore Port Phillip.

Tuckey's report, and Collins' own dissatisfaction with the site chosen, prompted him to write to Governor King, seeking permission to remove the settlement.

When King agreed, Collins decided to move the colony to the Derwent River, on the island of Van Diemen's Land (Tasmania).