Blue Shark Adventure - Jonathan joins Charlie Donilon on his shark charter boat in Rhode Island, Massachusetts, and learns about how shark tagging has shed light on the biology of and behavior of Blue sharks. Tagging has shown that these incredible swimmers actually migrate completely across the Atlantic ocean. Jonathan tries his hand at tagging a shark and then swims with Blue sharks. We also learn that Blue sharks are not nearly as vicious as they have been reputed to be, and the divers are actually able to pet the sharks! The most exciting moment comes when a shark accidentally gets into the cage, and Jonathan must figure out how to rescue it without getting bitten. Underwater Cavern - In a quiet forest in central Florida, a mysterious pond filled with warm clear water hides a secret at the bottom. Jonathan explores the pond to find a spring which leads into a cave. As Jonathan travels underground, he meets unexpected marine life in the dark depths and learns how water travels through an aquifer from the underground world to the surface. Giants of the Depths - The Sperm whale holds many records. It is the deepest-diving whale on Earth, the largest toothed whale on Earth and has the largest brain on the planet too. On top of that, it has a reputation for being a vicious beast, thanks in part to Herman Melville's Moby Dick. But the real Sperm whale is a lot different than people think. It has a highly-evolved social life, operates at depths where nobody can see them most of the time, and uses sonar which is so sophisticated that it makes the Navy's electronics look like toys. Sperm whales are very hard to find and even harder to film. In the Caribbean, Jonathan repeatedly attempts to get close to the elusive whales, until finally he succeeds and has an incredible experience eye to eye with a giant who investigates him with powerful sonar clicks.