Imagine producing a bubble with pippete or something similar into a normal tap water at the bottom of a 2m high cylinder. Or maybe even oil; that would result in in bubbles being rounder even at little bit bigger radiuses because of surface tension if I'm correct (easier to conduct an experiment)
Hi! As we know air bubble in the water rises due to buoyancy and quickly reaches its terminal velocity. What is more, as bubble rises the pressure decreases, consequently the volume of the bubble increases resulting in buoyancy becoming larger. So the terminal velocity doesn't remain constant...