Human beings breathe as a reflex; dolphins do so consciously. In the same way that we decide to walk, they decide to breathe. When they rise to the surface, they fill 80-90% of their lungs with air so that they can stay underwater for a long time. Breathing while asleep is no problem for them, for they use their brain’s right and left lobes alternately for 15-minute periods. While one lobe sleeps, the other is on duty so that the dolphin can ascend to the surface and breathe.
Human beings are not the only entities on Earth with complex features. Just about everywhere you research and investigate, you can see countless complex and varied life forms flying in the sky or living in the depths of the oceans. The way that they have been created differently from us and from each other, as well as in different kingdoms, is part of the wisdom of Allah, the Creator of all distinct works and beauties.