What are we seeing?

It’s the water.

The surface of the bubble is acting like a mirror, so you are seeing a image of whatever is at a certain angle between your eye and the bubble surface.

Air in the water is basically displacing the water, the same way a boat displaces the water. It is displaced for the amount of space required for that air to occupy. If a boat could be invisible you would be able to see the displaced water as a depression on the surface. And as @stranger_in_a_strange_land states, the surface of the bubble reflects outward, and the difference in molecular structure of the two elements are what enables the air to remain a “solid” until it reaches the surface where it disperses.

I see tiny universes birthing and dying, birthing and dying, birthing and dying…

The curved surface of the bubble, caused by surface tension, refracts and reflects the light.