underwater breathing

When humans can swim freely underwater like fishes, what new things will appear in life on this Earth?

So if in the future, when the Earth is submerged in sea water, we don't need to be too worried.

We know that frogs are amphibians that can breathe through their lungs and skin. But when they were tadpoles they lived completely under water.

Humans and other airborne organisms often drown when there is too much water in the lungs, but Russian scientists have demonstrated that a dog can survive underwater.