白手起家的富豪刘轩（邓超 饰）新拍下了一块地皮，并联合了女强人李若兰（张雨绮 饰）使用恐怖的声纳技术驱赶鱼类，用于填海造地。人鱼一族长期居住在附近区域的海里，为了继续生存，带头大哥章鱼八哥（罗志祥 饰）派出了美人鱼珊珊（林允 饰）“色诱”刘轩，准备刺杀。没想到珊珊在卧底过程中与刘轩暗生情愫，一次次破坏暗杀计划，而李若兰却在准备一个更丧心病狂的邪恶计划……Xuan's estate project involving reclamation of the sea threatens the livelihood of the mermaids who rely on the sea to survive. Shan is dispatched to stop Xuan and this leads them into falling for each other. Out of his love for Shan, Xuan plans to stop the reclamation. Unfortunately, Shan and the other mermaids are hunted by a hidden organisation and Xuan has to save Shan before it's too late...