Dr. Craig O’Connell and shark photographer Andy Casagrande travel up the Serena River in the rainforests of Costa Rica to try and find out why young bull sharks swim up the river, and how they avoid the very large American crocodiles living there.
By entering your email address, you agree to our Terms of Use and acknowledge the Privacy Policy. discovery and its affiliates may use your email address to provide updates, ads, and offers.
To withdraw your consent or learn more about your rights, see the Privacy Policy.