Your underwater eyesight?
Light is strongly refracted [redirected] in water in comparison to air.
You can see the effect by putting a spoon halfway into a water bowl
and you will see the water seemingly bend the spoon's image.
That effect [refraction] underwater can also enhance your eyesight by
focusing light; acting as....a water lens.
You can theoretically make telescope lenses out of water
contained in other transparent materials.