Dr. Callum Caldwell was always fascinated with the sea but tragedy drew him much closer to it. Struggling with his own issues, he makes his life swimming in the sea and doing research. Deep down, he finds himself missing something in his life. Lonely, he goes on a trip with his family and finds himself constantly being watched by something. Meanwhile, several feet below the ocean, a merman named Kai is fascinated with humans and wants to get to close to one. When he sees Callum, he is instantly drawn towards him and the two eventually become friends. Kai soon realizes that they cannot keep living with one on land and one in the sea. Therefore he makes a deal with the witch of the sea; he needs two months to fall in love with Callum and Callum must love him in return. If he can't do this before midnight on the last day, he will sacrifice himself to the sea. As time passes, the two start growing closer and Kai begins to fall for Callum. However, he can't tell if Callum is in love with him. Through many obstacles, the two realize they can't stay like this forever. Will they be able to be together or will something out there keep them apart?