How do Sharks Breathe?

9. How do Sharks Rest?

Scientists believe sharks that breathe only through obligate ram ventilation use features of the water to rest without drowning. Temperature, salinity, and time of day affect the oxygen concentration of ocean water. Scientists discovered motionless reef sharks in the Caves of the Sleeping Sharks during the 1970s. Reef sharks breathe with obligate ram ventilation. The scientists theorized that the exceptionally high concentration of oxygen in the cave waters allowed the reef sharks to remain still.