The monohull vessels are named M.S. "Marin", M.S. "San Francisco", and M.S. "Sonoma". The Marin can carry 750 passengers, and the San Francisco and Sonoma can carry 630 passengers each. They were purchased from Philip F. Spaulding & Associates in San Diego in 1976–1977. They were originally powered by gas turbine water jets but were converted to diesel engine propeller drives in 1983–1985. More efficient diesel engines were installed in 2001 and 2002. The "Marin" was refurbished from November 2006 to July 2007.