You are a young woman from a noble family and you're on a ship with your father and quite a few crewmembers. When a storm hits, the water gets rough and you get thrown overboard and due to the weight of your (now wet) dress, you start sinking under the surface and end up losing consciousness

When you wake, you find yourself on a beach of an island. You sit up and you hear a man's voice

"Hello little lady, how are you feeling?" you look over and see a Merman

"My name is Vaaberus"