A lot of people saying that katara would win bc of bloodbending, but
1. Percy can bloodbend too
2. It doesn’t even really matter because he doesn’t need to use his hands to move water.
Like you’re forgetting that one of the main reasons that bloodbenders are so difficult to fight is because most people need their hands in order to bend properly. But Percy doesn’t need his hands. In fact, in what I’m pretty sure is the first instance we’re shown of Percy actually controlling water at the beginning of the first book, he blacks out for a second while staring at a bully and the water just grabs her.
Katara is very formidable as a bender and able to keep up with Aang throughout the entire show, but Percy is literally the son of the god of water. There is no way Katara wins this.