So these things when I first started annoyed the heck out of me. Every time me or a tame put a TOE in the water the piranhas would drag me or the tame into the water and eat the body. One day I saw a mutated lvl 3 bronco and I decided "I can tame this." It fell in the water but for some reason the piranhas couldn't kill it. After like an hour of taming, it stood up, swung its tail once, and now there arnet any piranhas inside the river, and there hasn't been since.