From Creatures Wikia
The Water Predators are another agressive grendel breed by Grendel Man. They are amphibious and can swim with the aquanorn swimmeragent. They are similar to the Water Element Norns due to the fact they do not feel homesick when in the sea. Babies are peaceful, adults will hit aquatic norns and ettins simply because they're bored. But keep them seperate from the norns and ettins, and they make a nice addition to any aquatic ecosystem. If you are playing with them in DS, the best metaroom to keep them in is the Aquatilis Pod or Aquatilis Caverna. C3 is required to see them properly, because the sprites are of the Jungle Grendels.