I just got my hands on Matthew Williamson for H&M's debut collection, but now it's all about the upcoming Summer line. Celebrities like Mary-Kate Olsen, Helena Christensen, and Olivia Palermo went all aboard The Majesty boat that was docked at the South Street Seaport in Manhattan. Pink neon lights shone while a performance by Grace Jones amped up the crowd. Those lucky enough to be on board were able to view the Summer collection on models who sashayed throughout the party. "I think it's an amazing collaboration and I think H&M makes really great choices in the designers they pick and Matthew is a given for H&M," said Helena Christensen. The line will be available May 14, but in the meantime, check out the Williamson-wearing attendees.