they suck it in through their ears
Gills
A shark obtains oxygen from the water using its gills.
Shark Bait
Fish use organs on the sides of their heads called gills. These organs are used to extract oxygen from the water around them, allowing them to breath.
ALL of the the organs in the human body need an oxygen supply. This even includes the organs responsible for delivering oxygen to the rest of the body: the heart and lungs. Every organ requires oxygen. All that can be said in this case is that some organs use/need more oxygen than others. For instance, the brain needs/uses more oxygen than the spleen.
The circulatory system takes oxygen from the lungs and carries it to organs such as organs in the digestive system. The organs then use the oxygen to help them function properly and give them energy.
Gills on a shark help it take oxygen out of the water.
death vision
Swimming helps to force water through the shark's gills, providing the shark with oxygen; the shark may not get enough oxygen otherwise.
Oxygen passes from the blood into organs through the wall of capillaries.
The organs most sensitive to deprivation of oxygen are the heart and the brain.
The gills of a shark (and other fishes) extract oxygen from the water, allowing the shark to breath.
The group of organs that take in oxygen from the air is called your respiratory system.