The Guppy Prince by C W Gray

Dover Rees is a guppy tailed merman and the youngest child of the King of the Southern Silver Isles. Despite the lofty title, he fits in better with the other guppy tailed working class than with his royal siblings. Dover spends his days secluded in his creek, successfully avoiding the King’s court and all the judgmental nobles there. Then, the most wonderous and horrible thing happens. He hears the mating call and knows his alpha is waiting for him.
Ben Elliot is just a human trying to get by in a small tourist beach town. He has his art and a few good friends, and that should be enough, right? Wrong. Coming home to a quiet house and an empty bed starts to wear on him, but none of the omegas he knows appeal to him. Until a storm knocks him off his fishing boat and he’s rescued by a mysterious, blue-haired omega.
Together, Dover and Rees forge a bond strong enough to stand against the storm of corrupt lords, court politics, and a cursed king.