Amphibians: how can frogs hibernate under water?

Self-tutoring about amphibians: the tutor mentions a lifestyle of some frogs.

I mention back in my post from July 3 about the green frog and how it can spend hibernation under water. I wondered how this works, but have since learned more:

Frogs can breathe through their skin: under water, during hibernation, such a frog can absorb oxygen by that method.

Source:

ontarioparks.com