In the movie Oceans Eight - in the scene when Weil tries on the necklace on Daphne they find out that the necklace can be opened only by the special magnet carried by Cartier's bodyguards.
However, during the actual heist, when Tammy finds the duplicate necklace and gives it to Daphne, they all agree that the necklace might have accidentally dropped into the water.
Even the Cartier guys seem to agree. Whereas, Cartier very well knows that the necklace cannot be opened without the special magnetic device.
So, how is it that Cartier casually agree or believe that the necklace might have slipped off ?