Marine mammals can dive for remarkably long periods because their bodies have evolved to adapt to the underwater environment.

Dr Chris McKnight has been researching how seals can hold their breath as part of his work at the University of St Andrews.

Gray seals may possess a secret sense that helps them survive at sea. The marine mammals adjusted their time spent underwater based on the amount of oxygen in the air they breathed before diving ...

The duration of each dive was positively affected by the availability of oxygen, but carbon dioxide had no impact. That showed the seals are not sensitive to carbon dioxide as other species may be.