Why can not I breathe underwater like fish?

Have you ever thought why we can not breathe underwater like fish instead of using oxygen cylinders and masks even though other fish are using oxygen to breathe just like we also use oxygen?

The main reason people can not breathe underwater is the difference in how oxygen is delivered in humans. When a person breathes, air travels from the nose to the windpipe and then into the lungs and the airways gradually tighten in the lung. Eventually, alveolae, Through which the oxygen passes through the membranes of the lung into the bloodstream and then takes out carbon dioxide from the blood and then outside the body in the process called exhalation.

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As for fish, they also need oxygen to survive, but they do not have a lung designed to extract oxygen from the air. Instead, the water is passed through its specialized organs, the gills that separate the oxygen from the water to enter the body of the fish and expel the rest of the other gases in the Water

But there are some marine mammals that live in water and do not have gills like whales and dolphins, and those marine organisms have a system to hold oxygen inside their bodies for long periods of time under water but ultimately need those marine organisms to rise to the surface of the water to exhal and breathe oxygen again