Wikipedia
The Kataw is one of the merfolk in the Philippine Mythology. In Visayan, Kataw was believed to have higher rankings than other water and sea creatures as those of Sirena, Sireno and Siyokoy. It is believed that the Kataws are the reigning rulers of the kingdom Bantay Tubig.
Based on physical features, Kataws, along the Sirena and Sireno, were the Bantay Tubig-creatures that bear likeness to human while Siyokoy are those that resemble water-creatures. Unlike Sirena, they have feet instead of tails but they have gills on their bodies and fins in their arms. These marine creatures disguises into fishermen asking for help. When approached by mortals, the Kataws drown them into the abyss.
According to old folks, Kataws have the ability to manipulate and control water-type elements and related forces such as pressure, tides, waves, bubbles and the likes. Also, they can change water to ice .