Once you have reunited an elephant with her herd, you can walk along the water until you see the prompt for photo #18.
Nadine will offer to snap the picture for you – a photo of Chloe pretending to touch the elephants.
The second photo of this chapter happens not long after.
Go up the stairs on the opposite side of the elephant herd area until you reach the rocky platforms. Traverse to the middle platform and walk to the edge for photo #19.