He joined HMS Sirius 28 October 1786 at Deptford, Crew Number 70, with no age or birthplace recorded. William wrote out his will on 18 March 1787. He was stranded on Norfolk Island, mustered on 20 March 1790 on Norfolk Island after the shipwreck.

William Bryant may have been the Master’s Mate who on the second day after the safe landing of the crew, the weather being more moderate, and the surf less dangerous, a few of the seamen, who could depend, in case of accident, upon their good swimming, were sent on board the ship wreck by the hawser, and the utmost exertion used to get some part of the provisions sent on shore; but it was the fifth day before any could be landed. Some crew members including able seamen Jacob Nagle and William Hunter who were known to be good swimmers along with a Masters Mate had been ordered back onto the ship to save as much as possible if not all the provisions.

Fellow HMS Sirius Officer, George Raper wrote whilst stranded on Norfolk Island:

We (Mr. Bryan, Mr. Shortland land, and myself), the only three non-commissioned Officers wrecked from the Simis (sic) that Capn. Hunter kept with the remainder Of the Crew, the others being returned to Port Jackson in the Supply (as before observed), had a most excellent Garden (our Garden of ab’t of an acre), which, though we did not clear from the Trees, we fenced round, dug up, planted, set and sowed, with the assistance of only one of our Seamen.

In February 1791, William returned to Sydney aboard HMAT Supply, disembarked on 26 February 1791.

He then embarked on the Dutch vessel Waaksamheid for England and discharged 27 April 1792.

References: TNA, ADM 48/4/35; Wreck of the Sirius, Letter from an Officer, Banks Papers in HRNSW, Volume 1: 397 – 402.