‘Tail-Standing’ Sperm Whales Snooze in Stunning Photo, Mindy Weisberger, Live Science, 24 July 2017

Photographer Franco Banfi was free diving … in the Caribbean Sea when he spied six still and silent sperm whales drifting in their upright postures at a depth of around 65 feet.
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Researchers first saw this unusual sleep behavior in sperm whales in 2008, [finding that] sperm whales dozed in this upright drifting posture for about 10 to 15 minutes at a time, and the whales did not breathe or move at all during their naps.
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Further observations revealed that the sperm whales entered these sleeping states by first descending head-down to a depth several times that of their bodies, then passively turning head-up and drifting closer to the surface. The findings showed that sperm whales around the world practice this vertical sleeping posture — but infrequently, spending only about 7 percent of their time asleep, which is less than any other mammal spends, according to the study.

7% of their time is sleeping. That’s only 1.7 hours a day!