Jonathan travels to Iceland to investigate a giant crack in the ground filled with frigid runoff from melting glaciers. It’s rumored to be the clearest water in the world. But to find out, Jonathan has to brave some very cold water. Next, he heads down to sunny Florida, not to dive a coral reef or a spectacular shipwreck, but to dive in shallow, murky water under a busy bridge. This secret spot is home to some of the ocean’s most remarkable, and weird, animals.