Pitt, 49, and his 9-year-old son were spotted boarding a police boat in Sydney Harbour Pier, which then took them to a yacht named Ghost. Wearing a tan blazer, gray T-shirt and khaki pants, Pitt waved to photographers as he guided Pax, dressed in a black hooded sweatshirt and shorts, to the dock.
The actor is currently in Australia promoting his new action film, World War Z, which Pax and older brother Maddox, 11, were allowed to watch for the first time at the London premiere earlier this month.
"My boys, they're big zombie fans," Pitt told Us Weekly at the June 2 premiere. "That's what first got me focused on the [Max Brooks] book and then the book started opening up other ideas . . ."
"It's just good summer fun," he added. "It's the most intense thing you're going to see all summer, I guarantee you."
Last week, Pitt and kids Maddox, Pax, Zahara, 8, Shiloh, 7, and twins Vivienne and Knox, 4, enjoyed a family dinner out in Berlin to celebrate Jolie's 38th birthday. "He's such a wonderful man and a wonderful father," the actress, who recently underwent a preventative double mastectomy, told reporters of her fiance. "I'm very, very lucky." Pitt spent the weekend promoting World War Z by making surprise movie theater visits in L.A., Atlanta, Chicago, Austin and Philadelphia.