How do whales go on long dives? 

Whales have unique adaptations that allow them to go on long dives. They are capable of collapsing their lungs during dives to prevent damage from the increasing pressure. To further protect their collapsing lung, they have a jointed rib cage that allows their thoracic cavity to collapse with their lungs.

Not only that, whales and seals have evolved to have high quantities of non-stick version of myoglobin — an oxygen-binding protein found in the muscles of mammals. This lets them store oxygen in their muscles in addition to that in the blood. This adaptation also allows them to maintain low levels of aerobic metabolism during their dives.

Deep-diving marine mammals limit the gas exchange from lungs to blood during dives. They do so to prevent excess nitrogen bubble accumulation, which could otherwise result in decompression sickness.

When diving, whales use their limited supply of oxygen strategically. They slow their heart rate down, which results in minimal flow of oxygen. To top it all off, several organs undergo anaerobic metabolism resulting in a redirection of available oxygen to organs, such as the heart and the brain. Unfortunately, anaerobic metabolism results in production of lactate because of which longer diving marine mammals have to spend more time at the surface to get back to the pre-dive lactic acid levels before going on another dive.