Would you live underwater?

Why can’t humans live underwater?

With everyone focusing on colonizing other worlds, maybe we could colonize other parts of the one we already have! Could we engineer ourselves to live in the ocean? Let's find out… and hopefully avoid anything hiding deep in the ocean.

So why can’t humans breathe underwater? 

Well, human respiratory systems were designed to get oxygen from air, which we need to live. Oxygen from the air you inhale makes its way through your body, eventually being absorbed by your blood.

Your heart then pumps that blood throughout your body to provide that oxygen to the cells of your tissues and organs. Carbon dioxide is produced and absorbed into your blood as the cells use the oxygen. This carbon dioxide is then eventually removed from the body as you exhale.

But the air people breathe isn’t just oxygen. In fact, the chemical makeup of the air you breathe is only about 21 percent oxygen. 

Since water is H20, a combination of hydrogen and oxygen, can’t we get oxygen from water then too? 

Unfortunately, no. To get oxygen underwater, we’d probably need to have gills like a fish. However, even the primary source of oxygen that fish get is not from the oxygen in H2O, but from microscopic bubbles of dissolved oxygen in the water.

Many different gases can dissolve in liquids, which you can see when you open up your favorite can of carbonated beverage! Fish extract dissolved oxygen out of the water using their gills. Their gills are designed to utilize that dissolved oxygen in water, which is found in far lower concentrations than in air. 

Also, if humans could be engineered to have gills, they might also need to take in more oxygen with their gills than fish to survive for a long time. While there would probably be other things to take into account, like a change in diet and pressure differences, breathing underwater is one of the biggest obstacles we’d have to overcome to engineer ourselves to live underwater.

We could maybe solve that problem if we could make humans with gills, or we could potentially still live  in the water if we could hold our breaths for significantly longer durations. This is the case with animals like dolphins and whales, who still get their oxygen from air like people do. 

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