Sudden and uncontrolled acsent.

[Blackwood]

Old Archemedies (did I come close on the spelling?) remember?

An object is buoyed by a farce equal to (the weight of the water/fluid the object displaces) - the weight of the object.

Close on both counts.

What Archimedes said is that any body submerged in a fluid is buoyed up by a force equal to the weight of the fluid displaced by the body.

He did not say that the buoying up force has anything to do with the weight of the object.




I think we all can agree that "buoyancy," at least from the perspective of diving or, say, a blimp, is the relationship between the buoyant and gravitational forces. If I was unclear when I seperated them, sorry.

 

[waterkitty]

as to runaway ascents, if you get behind the ball and the gas in your
BC starts expanding as you ascend, it will get away from you.

Well said, Andy. It happens also if you are following the bottom and it becomes gradually more shallow...if you are not keeping attuned to your buoyancy and not dumping air from your BC when you need to, the air expands and up you go. I should know, it's happened to me.
You just have to pay attention to the depth and to your buoyancy.