I don’t know and I don’t want to know it stepping on it. I found this article in a russian website

Translation:

A shocking video of an unknown creature living in the sand on one of the popular beaches near Vladivostok fell into the hands of independent experts. The inconspicuous white tube in the sand did not cause concern until the incident, which, according to eyewitnesses, occurred with a tourist from Asia.

“As we found out through our channels, the creature almost grabbed the Chinese man’s leg at the ankle when he unsuccessfully stepped on the “tube”,” an independent researcher from Vladivostok shares with us, “they tried to hide the incident in order to prevent panic, now we can assume “that the swimming season will be officially closed this year” The video of the creature being removed from the sand was obtained by independent researchers from an anonymous source in “science” and quickly became available to the networks, with comments from experts and recommendations to refrain from walking on the sand.

“Right powerful jaws are hidden in the sand around the “pipe”, working on the principle of a trap. The 3-meter tail, buried deep in the sand, does not allow the victim to escape,” the expert explained.

Anyway, there are still a lot of unknown creatures in the seas and not all are friendly, because of this I prefer to relax in Woods and Montains.