The Ushi-Oni (“cow demon”) is said to be found in many different areas of Japan, but the San’in region is haunted by an aquatic version of this monster.

According to The Obakemono Project:

On the coasts of Northern Kyūshū and the San’in Region adjacent to the Sea of Japan, the ushi-oni is thought to dwell in the ocean. Its appearance on the shore is preceded by that of a woman, who may be the monster called nure-onna or iso-onna or a transformation of the ushi-oni itself. She holds a child which she presses on passers-by, asking them to take it and give it something to eat. In the usual ubume pattern, the child becomes enormously heavy and stone-like when held, impeding the unfortunate person’s movements and giving the ushi-oni a chance to attack.

Given its proximity to water, the San’in region has long held many beliefs about youkai that live in the ocean. Similarly, there are many Kami-sama associated with safe sea travel and fishing.

One the JR Sakai Line in Tottori, (the train line between Yonago and Sakaiminato), many of the stations are themed around different youkai. This is how I first learned of this particular one–so as to say I have not had personal experience.