Clam worms are also used for fishing bait, according to Walla Walla University, who reports they put up a fight by squirming "violently" and sticking out their proboscis and jaws to try and bite. Their bites can be painful, per Seashore to Forest Floor.

What are biting sea worms?

"Sometimes called clamworms, these animals that ordinarily live on the seafloor undergo an incredible transformation under new and full moons in spring – their bodies morph into reproductive forms called 'epitokes' as they swarm in coastal waters," the agency wrote. ...

Do marine worms bite?

Swarms of hook-jawed sea worms have been spotted along the South Carolina coast and the state Department of Natural Resources says yes, they bite.