Dylan Dreyer returns to some of Earth's most extreme islands, from the Amazon River islands to the Philippines, getting up close with fascinating creatures -- from squirrel monkeys leaping around in the Amazon to fireflies illuminating the night sky.

Dylan Dreyer revisits the Amazon River to explore what lives in the water and on the islands, including a fishing trip with some locals and a run-in with two of the Amazon River's biggest mammals -- the giant river otter and the Amazonian manatee.