We know that one of the most important survival techniques used by animals in winter is hibernation. Aestivation or estivation is the hot weather equivalent of hibernation though not as common as hibernation. This is the technique used to survive hot summer days. All these techniques involve undergoing physiological changes within the body so as to survive.
Lungfish is one good example that practices aestivation. Lungfish has a swim bladder with blood vessels running around and connected to mouth, that functions like a lung. It breathes air at the surface, using air instead of water as a source of oxygen. Thus it is adapted for using oxygen regularly at the surface, instead of using oxygen dissolved in water.
In such a case, imagine what happens when the pool dries up? A lungfish burrows into the mud secreting a protective coating of slime around its body. The mucus or the slime dries into a sack that holds moisture in. It now breathes through a small air hole even though the mud dries up completely. It can as such live without water for as many as three years. It comes back to pool after rains. During aestivation, metabolism, respiration and heart rate fall to lower rates to some extent.