Some species of lungfish only breathe air and have no gills, and will drown if forced underwater..?

Question

Why might it be an advantage for lungfish to breathe air even though they live in water?

Answer 1

Doesn't that answer your question...

No way to breathe underwater...

Forced down under water...

Answer 2

Yes. They have to come up to the surface for air. If they are prevented to surface they will drown.

Answer 3

The water the lungfish does live in has extremely low oxygen levels.  Having gills is simply of no benefit to them.

Answer 4

The African and South American lungfishes use their lungs to breathe air while they are dormant in mud in times of drought. The Australian lungfish uses its lung to breathe air when the water is stagnant.

so they need to breathe air as they are not always in water, or at least not water which could support life.