Most aquatic animals have for breathing while most land-dwelling animals have
gills; lungs
spiracles; lungs
lungs; spiracles

gills; lungs

Marine animals have gills because of its physiological fitness in the environment. These animals have evolved to develop this type of organ in order to survive at the water while the lungs where organs that was developed for the land animals since there is the absence of water. 

Ithink that its like 15 mph.