The worm on the right is a tug worm. It burrows backwards into sand or crevices in rocks, coral, or sponges, lining its burrows with its own feces, which harden into cement. The hairs are angled frontwards for greater grip, keeping it from being pulled out. Passing animals may be grabbed in its twin tongues and devoured. These tongues are made of very tough, fibrous material and are kept sharp by running the tips through the two holes on the top of the animal's armored head. Those are not eyes, but sharpening holes. The creature has no eyes.
Tug worms often live in large colonies and this allows them to ambush larger prey. The tongues are so sharp they slip right through flesh and wrap around bone, pulling the prey toward them. Multiple worms holding on to the victim with their tongues and gripping their burrows with their hairs hold the prey in place while they take turns unwrapping their tongues so they can take a bite.
One woman once brushed by an outcrop of coral had her arm bones grasped by three tug worms and lacked the strength to pull them out from their burrows. Fortunately, she had her knife and was able to cut the worms' heads off - though this took several minutes as they are very tough creatures. Her arm later had to be amputated due to infection.