What is an Antibubble?An antibubble is the opposite of a bubble. A soap bubble in air is a thin film of liquid surrounding air. An antibubble in liquid is a thin film of air surrounding liquid.
Note that an antibubble is different than an ordinary air bubble in liquid. An ordinarry air bubble is simply some air surrounded by liquid. An antibubble has liquid inside and outside. They form when a "boule" or water droplet presses through the surface with a thin coating of air. This is nicely illustrated to the right in the drawing from Chang.
What Are Some Properties of Antibubbles?Since they are mostly water with a very thin skin of air, antibubbles are just slightly lighter than the surrounding fluid. This is how you can easily spot one. Ordinary air bubbles quickly rise to the surface; antibubbles take a long time to rise to the top. In fact, if the inner fluid in an antibubble is somewhat heavier than the surrounding fluid, the antibubble will actually sink. When an antibubble pops, all that remains are some very tiny air bubbles that rapidly rise.