BAD IDEA
If I pee in the sea, do the fish notice?
Yes, fish notice, but they probably won’t care unless you’re a walking aquarium of pee.
If you pee in the sea, fish can detect the chemicals because water carries smells very well underwater. However, ocean fish are mostly busy and evolved to ignore random stinky blobs passing by. So yes, they notice chemically but no, they won’t throw you a welcome party or an intervention. Still, leaving your yellow souvenirs in the ocean isn’t exactly the classiest way to mingle.