The 21-year-old, who attended the shark drama's Tuesday night (August 13) premiere in Los Angeles with the "Rocky" star, her sisters Scarlet and Sophia, and their mother Jennifer Flavin, was always on the phone with dad, chatting about tips and preparations, before she went diving each day.
Director Johannes Roberts insists he had no problem with her leaning on the Oscar winner throughout production.
"I think him (Sylvester) and Sistine would chat every day on FaceTime," the filmmaker shares. "He would say, 'This is what you should be doing...'"
But, according to the young actress, dad's input wasn't always helpful.
"He wanted the director's note to be: 'Instead of swimming away, confront the shark head-on...', which I don't think would've play out well (sic)," she tells Entertainment Tonight.