Yes, I actually checked to see if I was wrong. I know "fish" is usually the plural form of... well, fish. But fishes is a real word and can be used under certain circumstances. In this case, I put "sleeping with the fishes". If I put "fish", both singular and plural would work. I wanted to make it more clear. And of course, "fishies" is informal. And while writing this here in the description, the word "fishies" is underlined in red while "fishes" isn't!

Music I was listening to: https://www.youtube.com/watch?v=WJW_ldC7sUA