They may seem calm, and won't be dangerous most of the time, but don't be fooled: They boast descent damage and godlike resistance, think of them as Rock Elementals of the sea, exchanging HP for numbers.
Just like elementals, they have a small aggro range, very slow movement speed and not the highest of the DPS. But if you get cornered, be ready to suffer a slow death by their stone-crushing jaws.
On the center make dunkleosteus quite the pest when trying to gather silica pearls or other deep water resources. If one is provoked by combat or getting too close other dunkleosteus will come to attack you from very far away and it is almost impossible to escape once they swarm you or your tame.