Mary Shelly films people with a hand-cranked, 8mm film camera. Yet within hours, she watches -- and hears -- her film using a 16mm sound projector. Apart from the difference in gauge (8mm vs. 16mm) a hand-cranked camera cannot record sound.
(at around 10 mins) During the shots of Emily talking while supposedly moving at a moderate speed on the boat, it is obvious the boat is stationary as the water directly behind her is hardly moving. A scene lasting a minute, surely a mistake.