What a wonderful video from a time so very long ago. Can you believe that this is what it used to be like here?

I will object to his use of the word "elastic" though. The glass generally breaks when used as a hammer because it is brittle, and the water prevents this (if the experiment is set up correctly) because it is (nearly) incompressible. It is not really meaningful to say that water is or is not elastic, because it is a fluid and elasticity is a property of solids (yes I know, compressible fluids are in some imprecise sense "elastic").

Rubber bands are elastic within the (wait for it) "elastic range," and metal and (definitely) glass are not elastic outside of the elastic range. However, it is a common surprising fact pointed out in any textbook with a title like "Strength and Elasticity" that rubber is surprisingly incompressible in comparison to its stiffness.

The surprising result with the bubbles can be read about here. For a more intuitive picture, imagine a small bubble sliced in half (so we are looking at a hemisphere). The inner pressure pushes in one direction (say up) with total force pi*(p_i)*(r_i)^2. The outer (ambient) pressure pushes the other way (i.e. down) with total force pi*(p_o)*(r_o)^2. If you drew your picture carefully, you will see that surface tension pulls in the same direction as the outside pressure, with total force 2pi*(r_av)*(s), s the surface tension per unit length.

If you assume that the thickness of the bubble is negligible compared to its radius, you will get that the pressure inside the bubble is 4*s / r_av larger than the ambient pressure. This means that small bubbles have a higher internal pressure than large ones, so that the bubbles do not equalize, as the host guessed, but the small bubble vacates into the large one.

Obviously, the demonstration of the principle of the submarine is presuming gravity is pulling everything downward, because the good professor is a "globetard" like all smart people are, lol.