Incidentally, a few nights ago on another night dive, we found and played with a couple of bobbit worms (Eunice aphroditois)...a nocturnal, predatory polychaete worm.
I first sought out and photographed these scary animals about a decade ago in Secret Bay, Bali. We stayed up most of the night, diving in dark, cold waters to observe bobbit behaviour.
At night, these worms lie in wait with their trap-like jaws wide open, hoping for fish or other unsuspecting prey to wander by. In one instance, I watched a bristle worm wander near a bobbit...only to be sliced into three pieces in the blink of an eye.
Bobbit worms have five sensory appendages on their heads, which probably detect nearby movement.
When something wanders too close, the worms lunge out and their jaws snap shut. The worms then drag prey completely into the ground...to consume their meals in the privacy of their subterranean lairs. Yuck.