Dolphins
Mammals not Fish
Even though they live in the ocean all of the time, dolphins are
mammals, not fish.
Like every mammal, dolphins are warm blooded. Unlike fish, who breathe
through gills, dolphins breathe air using lungs. Dolphins must make
frequent trips to the surface of the water to catch a breath. The
blowhole on top of a dolphin's head acts as a "nose," making it easy for
the dolphin to surface for air.