The steel-hulled, diesel-powered yacht Aras was laid down on 19 March 1930 by the Bath Iron Works; launched on 8 December 1930, and delivered to wood-pulp magnate Hugh J. Chisholm, Jr., on 15 January 1931, who named it for his wife, the former Sara Hardenbergh.

Rear Admiral James L. Kauffman, the first commandant of NOB Iceland, had arrived in Reykjavík in the battleship Arkansas shortly after the United States entered the war.

When Camp Knox – the naval facility on Iceland – was completed in mid-May, Kauffman hauled down his flag and moved ashore to release Williamsburg for other duties.

With the inspection trip completed by the end of May, Williamsburg put to sea to contact the disabled merchantman SS Gemini, reportedly suffering from a damaged propeller and under tow by the British tug Jaunty.

While en route, a PBY provided air coverage; the gunboat sank a drifting mine with machine gun fire.

After transporting a party of Army officers and nurses to Hvalfjörður and back to Reykjavík for an inspection trip and a visit to the battleship Washington, Williamsburg operated on local patrol and convoy escort during July 1942.

On 12 July, in the midst of one such mission escorting the liberty ship SS Richard Henry Lee, Williamsburg took on board 28 sealed boxes of gold bullion – valued at approximately $1,500,000 – at Seyðisfjörður, and transported it to Reykjavík, where she turned it over to Washington.

Williamsburg again served as a VIP transport the following month, taking a USO troupe to Hvalfjörður, where the entertainers put on two shows on 2 August.

While en route, she received dispatch orders to rendezvous with the merchant vessel Medina and screen her at Höfn, during the cargoman's unloading.

The gunboat proceeded ahead without sonar (it had developed a casualty en route) and with both depth charge tracks badly sprung.

Underway for Seyðisfjörður, on 22 September, Williamsburg spotted an unidentified four-engined bomber overhead at 08:30 but, due to the mist and rain, could not identify the plane.

The gunboat subsequently escorted SS Lochnagar on revictualling missions to Búðareyri, Seyðisfjörður, and Akureyri, before she returned to Reykjavík, later in the month.

Following further coastwise convoy escort runs in November and December, Williamsburg underwent a tender overhaul and availability alongside Vulcan through Christmas of 1942.

After getting underway for New York Harbor, on 7 February, the gunboat touched at St. John's, Newfoundland, en route and was briefly diverted to Argentia, to escort Pontiac.

Instead, Williamsburg's new employment was to be that of presidential yacht, to replace Potomac, the former Coast Guard cutter and a long-time favorite of the late President Roosevelt.

Re-embarking the Chief Executive at Yorktown later that day, Williamsburg touched at Norfolk, and Annapolis, Maryland, before she returned to the Washington Navy Yard to disembark the President on 18 May.

Among the modifications was a seawater aquarium for preserving live specimens and a lab equipped with microscopes and other instruments for examining and classifying samples of marine life.

Renamed Anton Bruun, in honor of the noted Danish marine biologist, the ship made ten scientific cruises in the Indian Ocean, conducting broad sample studies of bottom, midwater, and surface life.

[1] Offered for sale by the Maritime Administration, the former gunboat, presidential yacht, and oceanographic vessel was acquired by a commercial concern whose intention was to use the ship as a combination floating hotel-restaurant-museum to be permanently berthed in Pennsville Township on the Salem River, in New Jersey.

There the yacht remained in the southern end of Pennsville Township, in Salem County, New Jersey, and for several years after that as a restaurant before being sold to new owners.

These plans were never realized, and the former yacht faced imminent scrapping at La Spezia, Italy, but an urgent appeal to the Italian government saved her.

[3] Williamsburg was laid up at the Navy wharf in La Spezia, Italy while offered for sale by Camper & Nicholsons International of Monaco.