Whales can not breathe under water. They can hold their breath for nearly two hours.
When they surface they blow out air as an act of exhalation.
(GBR Explorer)Breathing in the sea
Whales breathe air through their lungs and therefore must surface regularly. Often the first sighting of whales in an area is the 'blow'. This is warm, moisture-laden air that condenses into water vapour to form a mist-like cloud when exhaled through the blowhole. Baleen whales have blowholes divided into two, while toothed whales have a single blowhole.
All whales can stay submerged longer when feeding or when in danger. The sperm whale can hold its breath for nearly two hours! It also holds the record for being the deepest diving whale - it can descend to three kilometres.
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