Bahamas Blue Holes - Jonathan travels to Andros, an island in the Bahamas, to investigate underwater caves that start in blue holes. A blue hole looks like a pond, but leads into a vast underwater cave system. In the Bahamas, these caves often lead to the ocean. As Jonathan explores the ocean end of the caves, he learns how the two systems are connected. Georgia Aquarium - Jonathan visits the Georgia Aquarium in Atlanta-the largest aquarium in the world-where they keep not one but four whale sharks in captivity, as well as two manta rays. Whale sharks are the largest fish on Earth and Jonathan learns how these animals are maintained in captivity while he dives with them in a 6 million gallon fish tank!