The Ancient Fish Grendels are a genetic breed of aquatic grendels designed by Grendel Man. All versions have long lives. They cannot breathe above water, and will drown fairly quickly if placed above water. They will able to swim with GM's Improved Swimming Agent. Their immune systems are weaker than a regular grendel's (except for the Dunkleosteus, which in that case is normal). They like to eat critter meat, but need to eat less than a regular grendel. The final change is the fact they will not usually use doors or elevators, due to the lack of the drives.