Sperm whales in the Arctic Circle seem to push out controlled streams of bubbles to help control their position in the water while at rest in a vertical stance.
Tagged animals included several large mammals as part of efforts to study resting patterns in the wild in their usual habitat.
The work hints that the whales' large heads do not really cause tipping or wobble while at rest.
A number of adult females have been spotted drifting inverted below the surface as a way to hold onto calories.
Posing like that could also help nursing mothers while away from the group, researchers say.
That documented habit add to the limited record of cetacean idle states, scientists add.