The species stands out from others by the black tip on the proboscis, a part of the worm that is twice as long as the collar, researchers said. “Glossobalanus weii sp. Nov. usually inhabits ...

The creature looks like it's a proboscis or ribbon worm, Kyle Hill of Nerdist explains - a Google translation of the video description from Thai to English seems to indicate the same.

When these worms 'mouth fight', a short proboscis extends followed by extremely rapid expansion of the posterior pharynx. This rapid strike produces a loud 'pop' comparable to those made by ...

They suggest that "when a worm begins to burrow in the sand, its resistance is first reduced by alternating extrusion and withdrawal of the proboscis and then the anterior end of the worm is ...