the door was only 6cm thick, and since it weighed in at 64.9kg then that plus the actors’ weight times the acceleration of gravity at sea level (9.81) comes out to 1926.684 Newtons, far greater than the 882.9N which is the maximum force that can be produced through buoyancy.
bottom line:they would have sunk.
HEY HEY, NO. Rose could have tied her life jacket around the bottom of the door to stay afloat.
They would have survived. (Proof? Watch Mythbusters.)
Mythbusters? I watched that, they’re both just chillin in normal degree water on a nice spring day. And then they’re like, “Hey maybe we can add more buoyancy by tying this life perserver to the bottom of the board?” Then they go up to Jim Camerons and tell him that and Jim Camerons is all “Whatever, Jack sposed to die mythbuster nerd, he gon die no matter what. Maybe the board should have been a lil smaller. I can do that digitally anyway.”