The title of the original article [1] is a lot more clear:

    Buoyancy regulation through modulation of onboard gas volume by resting sperm whales

If you've done any scuba diving (or swimming) you're familiar with this method of buoyancy control. And most fish accomplish on actively transporting gas between an internal bladder and their blood.

The difference is that whales have no way to refill their lungs while submerged, which is why their dives start deep and slowly drift up: as long as they are drifting upward the volume in their lungs is expanding in response to decreasing pressure. So the bubbles are essentially a way of pumping the breaks, which is apparently something they can do in their sleep (if they are in fact sleeping).

Is anyone else slightly annoyed by the cutesy title? Of course I recognize that the meme economy runs on this stuff, so maybe it's just nerds like me.

[1]: https://dmscdn.vuelio.co.uk/publicitem/61eae467-9527-4922-b9...

> They don't "blow bubbles" to sleep vertically, they vent gas to regulate their specific gravity. This allows them to sleep vertically

When I read this I thought you'd discovered that the whales release the gas in a form other than by blowing bubbles, or that the purpose of doing so was for something other than improved sleep.

But no, the whales literally release air through their blowhole in the form of bubbles, and, at least during study you linked, they do this while resting to maintain their vertical orientation. An orientation, the paper theorises, that enables better sleep by not being buffeted by waves.

They quite literally blow bubbles to achieve restful, vertical sleep.