The designer, known for his slinky knitwear, sparkle and print, has signed a three-year deal with Freemans Grattan Holdings, a division of Otto Group.
Paris Hilton, Caroline Stanbury and Jodie Kidd were among the drivers to attend the fund-raising gala at the V&A museum in London.
Badgley Mischka, a label known for red-carpet dressing, will hold two runway shows at sea.
Macdonald and Topshop Unique are the latest brands to rejig their priorities and change up their show formats.
Just in from a QE2 transatlantic crossing, Julien Macdonald also helped debut a new fashion-themed in-flight film for Etihad Airways to kick off NYFW: The Shows.
The British designer created a limited-edition printed box for the fast-food chain.
The 1,130-square-foot boat will depart from Southampton, U.K. on Aug. 31., and arrive the Brooklyn Cruise Terminal.