It lived in shallow waters and had a fish-like tail, and although it was distantly related to modern day crocodiles (the eusuchians), Metriorhynchus became completely aquatic: its feet became flippers and it lost the body armor typical of the crocodilians, so its only hope of escaping predators such as Liopleurodon was its speed.
Unlike other crocodiles, Metriorhynchus gives birth to several live infants. The mother probably did not take care of her young for very long. They spent most of their time in shallow waters catching anything their size allowed. But sometimes Metriorhynchus came to deeper waters, though this was very rare, usually when hunting the giant fish Leedsichthys.