When Sylvester goes to the nurse's station to get seasick remedy for the 2nd time, Tweety pours nitroglycerin into the bottle before Sylvester enters. Sylvester then picks up the bottle and starts drinking out of it. The next shot shows Tweety on a shelf with the same bottle underneath him. Then in the next shot, the bottle is back in Sylvester's hand.
After Sylvester steals Granny's glasses to paint Tweety on the lens and attempts to steal Tweety from the cage, when Granny puts on her glasses, Tweety is painted on the wrong lens. Sylvester had just painted Tweety on the opposite lens.
The door of Granny's cabin appears to be louvered on the outside, but not on the inside - or on the outside when the door is open (and visible from the inside).
When the ship.is shown going up and down over some rough seas there is no smoke coming out of the 2 funnels.