[1] In October 1903 she joined her sister ship Prinz August Wilhelm on HAPAG's route between Hamburg and Mexico.

[5] In September 1905 the Royal Mail Steam Packet Company (RMSP) announced that it would start running a fast passenger service between New York and Jamaica.

[9][10] On 5 June 1907 Prinz Joachim reached New York from Central America carrying passengers including former President of Honduras Marco Aurelio Soto, and the US explorers Hiram Bingham III and Alexander H. Rice Jr.[11][12] On 4 November 1909, just after Prinz Joachim docked in New York, the Purser's personal steward let himself into the Purser's office, unlocked the safe, stole $8,065 in US currency that passengers had entrusted to the Purser, and then absconded from the ship.

[14] On 9 January 1910 Prinz Joachim was leaving Kingston for Colón when she ran aground on soft mud.

[15] The next day both her sister ship Prinz Eitel Friedrich and Hertha tried to pull her free, without success.

Prinz Joachim was in Puerto Limón at the time, and contributed her ship's doctor and five of her stewards to a relief expedition that was sent by train to Cartago.

At the end of the operation, a high sea drove one of Prinz Joachim's boats off course, and prevented it from returning to the ship.

[25] The Norwegian steamship Fritzoa rescued the second officer and his crew, and landed them at Felton, Mayarí, Cuba.

[26] Seguranca took the passengers to Nassau, Bahamas, where all but eight of them were transferred to the Ward Line steamship Vigilancia.

[29] The Lindo brothers of Jamaica, who were to supply Atlantic Fruit from their Costa Rica banana plantations, withdrew from the partnership, but a month later Prinz Joachim was still maintaining the service.

[30] For the season from September 1912 to January 1913, HAPAG advertised Prinz Joachim making round trips from New York to Fortune Island (now Long Cay), Santiago, Kingston, Colón, and Puerto Limón.

However, at 11:00 hrs that morning, with the First World War imminent, HAPAG announced the suspension of its Atlas Service.

Prinz Joachim's passengers were transferred to RMSP's Orotava and United Fruit's Pastores.

[35] The company considered selling them to US interests, so that they could return to service registered in the then-neutral USA.

[36][37] HAPAG also offered to loan Prinz Joachim to the American Red Cross for up to two months, on a non-profit basis, for $1,100 a day.

The US government anticipated that if it went to war with the Central Powers, merchant crews of those countries might sabotage their ships to prevent the USA seizing them.

On 12 May therefore, 70 United States Customs Service inspectors searched German and Austro-Hungarian ships in the Port of New York and New Jersey for explosives.

[41] On 3 February the Navy Secretary ordered the seizure of all Central Powers ships in US ports.

[citation needed] On 26 February 1918 the US Navy commissioned her as USS Moccasin, with the Naval Registry ID-1365.

Late on 31 December 1918 she reached Gravesend Bay from Brest, France, carrying explosives and troops.

[49] On 15 August 1919 the USSB invited bids to repair her and convert her to burn oil fuel.

However, the USSB Chairman, John Barton Payne, ordered that liquor would not be sold on its ships.

[52] Moccasin called at Saint Thomas, U.S. Virgin Islands and Rio de Janeiro, and reached Buenos Aires on 26 January, 25 days after leaving New York.

Argentinian newspapers praised her passenger accommodation, but commented on how small she was, and that she looked "unpainted".

[58] Payne admitted to the Congressional Commerce Committee that the liquor ban compromised the viability of the new service to South America.

[59] Shortly after her return to New York, Moccasin partly sank at her berth in the Erie Basin at Red Hook, Brooklyn.