Built in 1944 for the US Navy, Calisto was originally a YMS-1 class minesweeper that was transferred upon its completion to serve the Royal Navy of Great Britain. After World War II and a decade of glorious service, her voyage soon charted a new course.

In 1954, she was bought by Mr.Thomas Loel Guinness, the Irish tycoon and former MP, who also owned the famed La Calypso of Jacques Cousteau. Under Mr. Guinness' dedicated supervision, Calisto was brilliantly transformed into his personal luxury yacht.
Just like La Calypso, her sister vessel, Calisto was, and still is, all about old world charm and high sea exploration. She catered to the boating pleasures of the elite and well-heeled. She sailed the waters of Greece and Britain, roamed the seas off the Antibes and Sicily and all over Europe in Style, often in the company of celebrities and politicians. In the late 1950s, a prestigious French Family purchased the Calisto and maintained the vessel for the next forty over years.