When the first victim is in the shower and her face and hand slide down the shower screen, the droplets of water are visible on the outside only, as there are no drag marks in the water droplets on the inside.
The ghost ship shows up in salt water, despite salt being supposed to repel spirits.
Sam's comment to Dean referring to "Miz" Case as "Mrs." Haversham should have been stated as "Miss" Haversham (from Charles Dickens' "Great Expectations").