Research teams studying whales near polar waters are seen releasing puffs of air in order to control their position in the water during short rest periods in a vertical stance.
A research group fitted sensors on nearly four dozen animals as part of efforts to study how they sleep outside captivity without disturbance.
The work hints that the whales' large heads appear not to throw off balance while suspended in place.
Several of the cows appear to rest inverted below the surface as a recovery method to conserve energy.
Posing like that may assist cows feeding calves in the gaps between meals, members of the team point out.
These shifts in buoyancy help broaden the limited record of how giants of the deep pause for hours at a time, scientists add.