Lime bubbles

I came across some finger limes at the markets. The flesh inside is almost like little balls: tapioca-like, but acidic and juicy. When we squeezed some lime balls into a glass of soda water, they travelled up from the bottom, bounced off the surface and floated back down again. I'm sure this has something to do with physics: the internal pressure of the liquid, the density of the lime flesh as opposed to the carbonated bubbles, the equilibrium and stability of the soda water.

(Note: obviously, the video is sideways...)