Question: what's the rarest fish you have seen?

I don’t think I’ve seen any particularly rare fish, and because I’m not into diving/scuba (I find it too claustrophic to enjoy it) I’ve not had the opportunity to see anything other what’s visible on the surface of the sea when snorkelling. I guess ‘rare’ depends on where you are in the world and what is ‘rare’ or ‘common’ for that location will vary according to the environment, whether you’re inland or on the coast, what’s happening to the local conditions/climate change impacts on fish ecosystems. I saw black tipped sharks in the Indian Ocean when snorkelling many years ago, but I’m not sure I’d call them ‘rare’ for that location, but if I was to see them off the coast of Scotland, where I live now, I probably would!