What strange scene does Abigail stumble upon when she reaches the shore? what is the significance of this image?

Abigail walks along the beach; she sees a baby sitting alone by the water. Soon she realizes that the baby is being photographed and she laughs. Abigail thinks about how the waves could sweep the baby away and none of the adults could do anything. This represents how Susie too as swept away with only one (the pervert Mr. Harvey) adult knowing what happened.