Characteristics - Blowholes
Since they are mammals, whales have lungs, not gills. They must come to the ocean surface to breathe through nostrils known as blowholes. Smaller whales can remain submerged for several minutes; however, the Sperm Whale can dive for up to two hours.
The first indication of the presence of a great whale is usually the sight of its "blow" or spout--a cloud of vapor produced largely by the atomization of water covering the blowhole during exhalation. A spout's height depends, to some degree, on the size of the whale and can often be used to identify species. After inhalation, the nostril automatically closes and the whale dives.
Baleen Whales have double blowholes; toothed whales have only a single nostril.
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