Okay, I KNOW it's supposed to be the koi, blah blah, but I wanted the name to match the other two. That being said, this was actually the first of the group and it was originally just going to be the animal companions of the respective benders (until I had no idea what Avatar Kiyoshi had) which is why it's Naga.
The symbol gave me a lot of stress, but I ended up paying homage to "The Great Wave" by Hokusai. I also tried to keep it looking like the water symbol and I dunno, I just spent way too long fixing this.
Avatar (c) Nick.
Image (c) me.