When Mr. Roarke pilots Margo Dean and Lowell Benson ashore the boat/couple are struck by a large wave. But both are more dry when Lowell carries her onto the beach.
A knife is thrown between Pierre and Janet, lodging in the wall in front of them, but upon turning around, the window is shuttered. The same kind of window on the upper floor is likewise shuttered but also has a screen and grid bars, which certainly would have been the case even more for the lower floor.
After Janet's hand gets covered with blood, she runs right past a fountain without washing her hand, intent on returning to the house to wash it in a sink.
Pierre, who describes himself as a French Canadian, clearly has an American accent and even more obviously has the Greek parentage that the actor playing him has.