Sharks are fish, and therefore breathe through the use of gills, slit

HOW DO SHARKS BREATHE?
Sharks are fish, and therefore breathe through the use of
gills, slit-like openings on the sides of their head.
Beneath the gills are tiny blood vessels that
extract oxygen out of the water as it passes over
them. Most shark species breathe by swimming
with their mouths open which allows the
water to pass over the gills. Some sharks
like nurse, angel and lemon sharks have
strong neck muscles that pump water over the
gills, allowing the shark to breathe while resting
on the ocean bottom.