Hmm, they seem to stop growing after they become adults... Fish don't, they keep growing all their life so old fish can get huge. Are shark people fish?
In a magical world, created by gods, evolutionary science struggles. They are both fish and mammals; they've got gills, their skin is more shark-like and is hairless, but they do have mammary glands and nipples. Their teeth even have different shapes, but the molars aren't as good at grinding and are much harder to see.
Besides, I needed to have a height limit so Puarani could be the little one.