This video says about itself:
15 December 2017
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.
JONATHAN BIRD‘S BLUE WORLD is an Emmy Award-winning underwater science/adventure program.