The wine bottle changes as Amber does charades.
When Guiseppe and Amber are back from the Island and the guy with the suitcase offers Giuseppe reward money, he wears a blue suit. Guiseppe angrily says he doesn't want his bribe; when the man returns to the bar with the suitcase ONE MINUTE later at the most, he wears a green suit. Pretty fast change.
When a tipsy Amber runs into Giuseppe in the hallway as the boat sways back and forth, exactly 20 minutes into the movie, the position of Giuseppe's hand on the giant dead fish he's carrying changes between shots.
Nobody ever credited The Cheerleaders/Marooned (1979) from December 1979 as original story, however the script similarities are too many to be a mere coincidence. In the TV segment called "Marooned", Jayne Meadows plays snobbish movie star Liz Merrill, shipwrecked with a meek man she despises but falls in love with him when he copes a very dominant personality, ordering her around.
When Guiseppe goes into the bar at the end after the first "bribe" by Amber's husband, he's wearing shoes; when he kicks the "re-suited" man out of the bar, he's barefoot. True, but his shoes Crocs-type clogs. He could have easily left them at the bar for ease of mobility when kicking out the re-suited man.
A camera and a pier are visible in closeups of Amber and Giuseppe stranded in the dinghy.