Bottlenose dolphins breathe air but can sleep in the ocean because
A) they cease breathing while sleeping and remain underwater.
B) they sleep for only 30 minutes at a time, which is the maximum interval they can cease breathing.
C) they fill their swim bladder with air to keep their blowholes above the surface of the water while they sleep.
D) they move to shallow water to sleep, so they do not need to swim to keep their blowholes above the surface of the water.
E) they alternate which half of their brains is asleep and which half is awake.
This is a still image from an animation of ocean surface currents from June 2005 to December 2007
Serotonin and the Sleep–Waking Cycle
Four pieces of evidence that the reticular formation is involved in sleep.
Ocean currents around the Antarctic
The five stages of sleep
Variations in the Ocean’s Surface Temperature and Salinity with Latitude