After leaping back into the water following a morning scuba dive, one woman realizes she has forgotten to remove her weight belt. Loathe to drop the lead to the bottom of the sea, she struggles to reach the boat ladder. A last fateful lunge positions her directly under the stern. As the boat rises on a lazy swell and drops sharply into the trough, it strikes her forearm -- snapping the bone -- and her head, knocking her unconscious. Her limp body drifts into the depths. Sometime later, her eyes spring open and she flails desperately to reach the now-distant surface. But just as she realizes she's breathing normally -- How can that be? -- she spots a dark shadow moving ever closer. Heart pounding, arm and head throbbing, she faces the unknown danger. The shadow materializes into a beautiful blonde mermaid who recognizes the dire situation and offers her help. A younger, shyer mermaid appears and between the two, take the injured diver to their community cavern. There, Serena as she becomes known, lives with the friendly, helpful Clan as her arm and head heal. Doctor Nathan, charismatically handsome with the greenest eyes Serena has ever seen, tends to her wounds and she's irresistibly drawn to him. Another mermaid, however, has been promised to the doctor and won't let an outsider usurp her rightful claim. She'll do ANYTHING to keep Serena from taking him away from her. After a verbal warning and several more sinister attempts to keep the couple apart, Nathan and Serena decide to leave The Clan and strike out on their own. The undersea world can be extremely dangerous when there are only two to keep other safe, but it's the only way they can be together. They find a safe haven and create a cozy home, living happily until disaster strikes. One catastrophic event changes everything and Serena must face an uncertain future.