Well, IMO that’s actually pretty easy to determine. I assume the pain you feel being cut by a hook is simmiliar to pain I feel being cut because we react the same way. Basically every living thing reacts the same way to cuts, yelping, bleeding then flight/fight. Cats, dogs, animals of all sorts go through the same steps when they are cut so it’s a safe assumption their pain is simmiliar. And things that don’t react, such as cutting a techincally alive potato, aren’t really feeling pain. Idk maybe potatoes silently scream, can’t disprove it, but that’s just not the same as creature that flee from threats

So while we don’t know what a fish thinks about suffocating in air, it’s a reasonable assumption that it’s similar to humans suffocating in water, unpleasant. We both thrash around and do our best to breathe again. Suee, in a philosophical sense it’s immposible to know what other creatures think, even other humans that can verbally communicate, but that ignores some of the more obvious context clues.