Use it as the turning point in a water or lake scene, after a splash or a soft magical chime and before the reveal that follows underwater. Let the next sound be a clear voice line or a bright magical cue, so the scene moves from the underwater moment to the discovery that follows.
About this sound
This 11-second clip plays the Harry Potter mermaid song, a soft echoing underwater vocal that sounds distant and submerged, like singing heard through deep water. It feels eerie and dreamlike, with a quiet mystery that makes the moment feel magical rather than playful. It comes from the films, where the mermaids sing their underwater secret.