A Water Cat?

Wondering around the King's Park together, I was trying to describe (in Thai) to two boys about the really big monitor lizards that live in the lakes and canals at this park. They guessed...bird? fish? water cat? Wait...did they just say "water cat"? What is a water cat? So, I ask G., who is their new mentor, what is a water cat? He does some hilarious actions, and finally makes attempts at the word in English, seal? A water cat is a seal!? The boys say, yes, they sound the same. Then after all of that, I wonder why they would think a seal lives at this park?