There is a slight difference in the scene where they first meet in the anime from the manga.
Little Lucia swims up to the surface to see what a ship looks like, and is amazed when she hears a clear, beautiful singing voice coming from a little boy on the deck of the ship. Suddenly, a tidal wave rocks the ship, and Lucia dives down to rescue the little boy who falls into the sea. She brings him to shore, and cries when he doesn't wake up so she uses her pearl to revive him. When he finally opens his eyes, he speaks to her for the first time, asking her who she is. This was Lucia's first love ♥
Seven years ago, little Lucia is enjoying the pretty fireworks going off from the cruise ship nearby, commenting that they look like flowers blooming in the sky. It was such a beautiful sight that she started to sing. A little boy happened to be out on deck and hears the beautiful melody, and she blushes when she overhears him say how beautiful her voice is.
He looks out into the ocean to see Lucia and asks what she is doing in the ocean, and when her sees her tail, he realizes she was a mermaid! Suddenly, a huge tidal wave knocks him off the ship, and Lucia quickly rescues him and brings him to shore.
She starts to cry when he doesn't wake up, so she uses her pearl to revive him. When he finally opens his eyes, he asks her who she is. Lucia is so relieved and happy, and realizes that she has fallen in love ♥