It was believed for many years that whaler sharks, such as this Caribbean reef shark, had to continually swim in order to breathe due to their weak gill system. Observations have proven that numerous species of sharks will actively rest on the bottom or in caves. It is still uncertain why this resting shark behavior occurs and if the shark is, in fact, sleeping. From my personal observation, we can only guess that this resting Caribbean reef shark was being cleaned by small fish and shrimp living in the cave. Learn more about the mystery of the resting shark behavior.