Can fish see the water ??? If human can't see the air, So fish......

This is an interesting question. The short answer is fish do not see water. Look at those adorable eyes.

The brain tries to filter out vision obstacles like a nose or filter out or constant vision noise like air. Our brains filter air, so anything with similar information, like air, will be filtered. Same with white noise, body noise, and smells. The brain filters this information to save processing power to focus and survive.

Seeing air, we can’t use color as reference information for it, so we use refractive indices. Water has a slightly higher refractive index than air, so we can see it.

Yet we evolved on land to filter out air taste, smell, noise, and look. Fish and sea creatures evolved the same way.

So the answer is no. They do not see, taste, hear or smell water because it is a constant environment noise.

Some water creatures took it further to filter out murky waters like this lobster.

See these segmented eyes.

Scientists were able to use their design to actually develop cameras that can see through fog or smoke for military purposes.

Questions like yours make humanity discover new things and developing new technologies. So keep wondering. :)

Update: for those asking can fish see air? No they can’t the same way you can’t see things with lower refraction index than air like helium. Air has lower refraction index so the eye can’t see it.