The sirena is one of the merfolks in Philippine folklore. She is depicted as half-woman from the torso upward and half-fish downward. Along with other sea creatures like kataw and syokoy, asirena has dominion over bodies of water including seas, rivers, and gulfs.
Here is a legend about a sirena from the province of Ilocos.
The sirena (or mermaid) is one of the most popular mythological sea creatures in the Philippines, especially in the Bicol and Visayas regions. They are perceived as beautiful young women with long alluring hair. With their unusual charm, they can lure their unknowing victims to their deaths. Their lower body is that of a fish and so they have dominion over the waters. They are often thought to be malign and cause unfortunate events like drowning accidents and boat wrecks.
Here is a legend about a sirena from one of the islands in Zambales, Philippines. -------------