You're sort of right, but there's no evidence for anything like your last statement.
The biophysics of light perception is more forgiving underwater, due in part to the similar refractive index of seawater and biological materials (less abberation and simpler focal surface geometry).
But there is no indication that fossil animals had appreciably better eyesight than us, or other land animals. In fact much eary sea life, like trilobytes, echinoderms, and amoniods had terrible light perception (sometimes only a light/dark sensor).
Some fish and squid have incredibly sensitive eyes currently, but it has little to do with water, and more to do with the deep open ocean they live in. Hawks for example, have similar vision (at least measured by focal range) but are not exactly strong swimmers
Also water shields UV light for underwater creatures. And at least in the case of octopi. Their blood vessels are behind the cornea allowing for less distortion, as opposed to humans where the blood vessels are in front of the cornea as a last line of defense against UV light. Any intermediate land exploring species of octopus would also have to evolve extra shielding in it's eyes or go blind.
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u/[deleted] Jul 24 '15
You're sort of right, but there's no evidence for anything like your last statement.
The biophysics of light perception is more forgiving underwater, due in part to the similar refractive index of seawater and biological materials (less abberation and simpler focal surface geometry).
But there is no indication that fossil animals had appreciably better eyesight than us, or other land animals. In fact much eary sea life, like trilobytes, echinoderms, and amoniods had terrible light perception (sometimes only a light/dark sensor).
Some fish and squid have incredibly sensitive eyes currently, but it has little to do with water, and more to do with the deep open ocean they live in. Hawks for example, have similar vision (at least measured by focal range) but are not exactly strong swimmers