Cleo's dad, Don Sertori, was acting out a pirate show and poked his sword toward Cleo, sending her careening off the plank into deep water. But in the first episode, Cleo said that she couldn't swim. Since her dad doesn't know about her being a mermaid, he would surely know that she was a non-swimmer. Yet he just resumed his act, ignorant of his daughter having just fallen in deep water. A child looking over the edge caught a glimpse of Cleo as a mermaid, and said so, and Don still didn't check on Cleo.