I don’t know shit about this, but some quick searching says that an air bubble would work better than glass as a lens underwater. The difference in refractive index is what creates the magnification effect:
Air: 1
Water: 1.3325
Glass: 1.52 (clear soda lime glass)
So .19 difference between water/glass, and .33 difference between air/water, making air/water the better magnifier.
I don’t know shit about this, but some quick searching says that an air bubble would work better than glass as a lens underwater. The difference in refractive index is what creates the magnification effect:
Air: 1
Water: 1.3325
Glass: 1.52 (clear soda lime glass)
So .19 difference between water/glass, and .33 difference between air/water, making air/water the better magnifier.
They don’t usually use that kinda glass as a lens for those purposes.
That said, I wonder what material lens would be better in water.