How do frogs adapt to breathe in water?

Like most other vertebrates, amphibians achieve air-breathing by drawing air into the lungs through the mouth or nose. Intaking oxygen underwater is different - this is done by diffusion across the skin membrane. Amphibian skin is very thin and permeable, oxygen in air or dissolved in water can diffuse through the newt's skin straight into the blood which is in tiny blood vessels (capillaries) close to the surface. BUT! permeability also works the other way, this is why amphibians must spend their lives in water or damp places to avoid dessication. The gills are replaced by lungs as they become adults