Open Water 2: Adrift (2006)

Continuity mistake: The baby's appearance changes drastically. When we first see her, she doesn't have a lot of hair. Later, she has a full head of curly hair.

Question: When Amy protests as Dan picks her up and jumps into the water with her, we cut to an underwater view of them plunging into the water together, and then Amy freezing up moments later. What happened that maybe triggered her the moment they went underwater?