I recall seeing, hundreds of years ago, a phenomenon called "bees wine". A highly clumping yeast would be inoculated into a sugary solution and the clumps would rise slowly from the bottom to the top and then slowly sink again. The object was to offer something fsscinating to interested kids, not to produce a decent drink.
I had always thought that the gas which the "clump" exuded remained associated with the clump, being held there by the "skin" of surface tension of the liquid at the interface of the bubble rather than going immediately into solution, When the clump reached the top of the liquid, some of the bubble was discharged into the atmosphere making the clump heavy enough to sink again.
Does this offer any insight into what might be going on in a vessel full of fermenting beer?
I have had beers (few and far between, thank Odin) where the vessel appears to be literally boiling- like the hard boil of a kettle. Touching the vessel indicated that, while it might be a bit warmer than ambient, it is by no means hot so the "churning" can't be fully explained by convection currents.
Edit:
Thinking aloud:
This would have implications for separating the quick "from the dead" using a fermentable medium provided the live-yeast-charged liquid were decanted off the rest of the dregs before the internal action became sufficiently violent to put the whole mass in motion. But it wouldn't help with the idea of simply rinsing the yeast in plain water.
That's all presuming I'm right with my "bubble" theory of course.