The king of the sea where Nehalaennia lived was Livyatan melvillei, a massive sperm whale. This sperm whale, with teeth measuring about 35–40 cm long, had the largest jaw ever – much larger and stronger than that of a Tyrannosaurus rex. Unlike a T. rex, this sperm whale could easily bite through a car. In the primeval sea of that time, many species of sperm whales swam, ranging from small to large, all with rows of sharp teeth. Each species hunted different prey, such as fish, seagulls, and seals. The largest and strongest among them, the up-to-18-meter-long Livyatan, likely hunted large whales like Nehalaennia.