Vanessa Hudgens and Gerard Butler spent a day on a boat together this past weekend.And it turns out they were among a small group of people who surprised their friend, Oliver Trevena, on his 40th birthday with an afternoon of partying on the Pacific Ocean near Malibu, California on Sunday.Butler and another mate helped lead Trevena, who was blindfolded, along a dock until they reached the small boat, where Hudgens and a handful of other friendswere waiting.