What animal is a koy?

"Koy" is not a recognized animal name in English. It is possible you have a misspelling or a word from a different language.

Could you please clarify what you mean by "koy"? Perhaps you're thinking of:

* Koi: A type of colorful carp, often kept in ornamental ponds.

* Coy: An adjective meaning shy or hesitant.

If you provide more context, I might be able to help you figure out what you're looking for.