Controversially, the ship did not have a marine chronometer on board, a comparatively new navigational instrument that was an "easy and cheap addition to her equipment" that would have enabled her to determine her longitude accurately.

Consequently, Arniston was wrecked when her captain headed north for St Helena, operating on the incorrect belief the ship had already passed Cape Point.

[citation needed] Arniston was heavily armed, with her fifty-eight guns[1] making her the equivalent of a Royal Navy fourth-rate ship of the line.

[8] The armament was necessary for the ship to protect herself and her valuable cargo from pirates and commerce raiders of other nations during long voyages between Europe and the Far East.

[2][non-primary source needed] On one of her homeward journeys from China, she struck an uncharted rock at 5°46′8″S 105°16′43″E / 5.76889°S 105.27861°E / -5.76889; 105.27861 (Oomowoomang), near the island of Pulo Goondy (modern day Pulau Legundi), located just south of Sumatra.

Captain Campbell Marjoribanks:[2] While Arniston was at St Helena on her outward journey, she undertook to transport troops from there to join Lord Elphinstone, who was undertaking an expedition to capture Cape Colony from the Dutch.

[10][non-primary source needed] Arniston was to ferry nine field pieces, as well as a company of artillery and three of infantry (393 men in all), to Elphinstone.

[11][non-primary source needed] On this voyage Arniston sailed under a letter of marque in the name of Captain William Macnamara, and dated 13 May 1797.

[5] Her itinerary was:[2] On this voyage Arniston sailed under a letter of marque in the name of Captain Campbell Marjoribanks, and dated 29 November 1799.

The objectives were two-fold: to avoid French ships reported to be in the Indian Ocean,[14] and to improve the charting of Bass Strait.

Compounding these navigational errors, the master had not taken any depth soundings (which would have confirmed his location over the Agulhas Bank), before heading north.

[6][17] Only six men (the ship's carpenter and five sailors[18] of the 378 people on board survived, after reaching the shore only with great difficulty through the high surf.

[6][19][non-primary source needed] A memorial, a replica of which can be seen today, was erected on the beach by the wife of Colonel Andrew Geils (spelled "Giels" in this instance), whose four children were lost in the tragedy on their homeward journey, having visited him in Ceylon.

[20] Thirty seven years later, the 73rd Regiment once again suffered hundreds of casualties on this coast when HMS Birkenhead was wrecked 50 miles (80 km) away at Gansbaai.

The wreck, which lies in about 6 metres (20 ft) of water, was surveyed by an archaeological team from the University of Cape Town (UCT) in 1982.

[21] The National Monuments Council issued a permit to UCT student Jim Jobling to conduct an underwater survey of the site, as well as a limited excavation.