Sharks cannot breathe on land; they are entirely dependent on water for respiration. Their physiology is adapted for extracting oxygen from water, making terrestrial environments incompatible with their survival.
How Sharks Breathe in Water
Sharks use specialized organs called gills to obtain oxygen from water. Water, containing dissolved oxygen, enters the shark’s mouth and passes over gill filaments. These filaments, rich in tiny blood vessels, facilitate oxygen transfer into the bloodstream while releasing carbon dioxide.
Water flow over gills varies by species. Some, called “ram ventilators,” must continuously swim with open mouths to force water over their gills. Other species, particularly bottom-dwelling sharks, use “buccal pumping,” actively drawing water into their mouths and pumping it over their gills, allowing them to breathe while stationary. Many sharks combine both methods, adapting to their activity level.
Why Land is Incompatible
A shark’s respiratory system is exclusively designed for water, rendering land incompatible for breathing. Gills, while highly effective in water, are delicate structures that collapse without buoyant support. This collapse significantly reduces the surface area for oxygen absorption, making it impossible for the shark to extract sufficient oxygen from the air.
The concentration of oxygen in water is substantially lower than in air, yet sharks efficiently extract a high percentage of it. Air, despite its higher oxygen content, presents a challenge because gills are not structured to process gaseous oxygen. Delicate gill tissues also rapidly dry out in the air, impeding gas exchange and causing damage.
What Happens Out of Water
When removed from water, a shark faces immediate, severe consequences due to its reliance on gills for oxygen. Gill filaments, deprived of water, stick together, drastically reducing their functional surface area. This quickly results in suffocation, as the shark cannot take in enough oxygen to sustain its bodily functions. Lack of oxygen causes rapid physiological stress and organ damage.
Survival time out of water varies by species and size. Large sharks typically last only a few minutes. Smaller species, or those adapted to shallow environments, might endure longer, from minutes to an hour. Prolonged exposure to air, even if brief, can lead to irreversible brain damage and death due to hypoxia.
Sharks With Unusual Adaptations
While most sharks cannot survive long out of water, certain species exhibit unique adaptations for short terrestrial excursions or tolerance to low-oxygen aquatic conditions. The epaulette shark, found in shallow tidal pools around Australia and New Guinea, is a notable example. These sharks can “walk” on their paddle-shaped fins across exposed reef flats between tide pools.
Their adaptation to low-oxygen environments includes significantly reducing their metabolic rate, heart rate, and breathing, conserving oxygen when trapped in oxygen-depleted pools. An epaulette shark can survive up to three hours in very low oxygen or briefly on land, but still relies on water for respiration to thrive. These adaptations allow them to forage in areas inaccessible to other predators, but they do not enable true air breathing.