After the grounding of his ships Gulnare and Wallaroo, for both of which he was held culpable, he turned his interest in photography from a serious hobby and part-time occupation to a profession.

As a result of this, during his return from the North Sweet organised exhibitions and lectures of his views surrounding the trip and secured sales of his prints through James Williams's Stationery shop.

In 1870 Sweet was also commissioned to supply northern construction teams who were building the British-Australian overland telegraph link from Darwin to Port Adelaide.

Previously a slaver in the Caribbean,[6] the 150-ton two-masted schooner was purchased by the South Australian Government in 1869 and refurbished as the Northern Territory supply vessel, replacing Sea Ripple, which had been condemned as unfit for service.

Gulnare, under Captain Sweet, left Darwin Harbour for the Roper River at 7am on 5 October 1871, and that same night she ran aground on one of the reefs that surround the Vernon Islands.

At an inquiry on 19 October Sweet testified that he was confident that Gulnare was sufficiently seaworthy to return to Adelaide, but the crew had deserted her to work on the Overland Telegraph Line.

At his studios Sweet took many portrait photographs but focused mainly on landscapes,[3] travelling around South Australia with a horse-drawn darkroom, taking pictures of the Australian outback and homesteads,[1] some of which were exhibited in Melbourne and Sydney.

On 4 January 1886 Sweet died suddenly due to sunstroke at "Halldale", home of the Hall family, near Riverton, South Australia.