How do seals breathe while spending long periods underwater?

Seals do not actually breathe while underwater; instead, they are highly adapted to hold their breath for extended periods during deep dives. For example, the Baikal seal can remain submerged for up to 40 minutes while hunting.1

These aquatic mammals possess specialized physiological traits that allow them to withstand the intense pressure of the deep ocean, which would otherwise cause a thoracic squeeze in humans. Key adaptations include:

• Elastic Chest Cavities: Unlike humans, seals have more flexible chest structures that allow their lungs to compress safely under pressure without separating from the chest wall.2
• Efficient Gas Usage: Their bodies are evolved to utilize gases in the bloodstream more conservatively, allowing them to manage their oxygen supply effectively during long dives.2

When they need to replenish their oxygen, they return to the surface or, in the case of ice-covered waters, use their claws to maintain breathing holes.1