Little Mermaid Reverse Fairytales

A tragic accident on the eve of her 18th birthday leads Princess Erica to a chance encounter with a mysterious man on the beach. When he turns up at her birthday party and whisks her off her feet, she knows she has to find out everything about him, but why won't he speak and where does he keep disappearing to? Ari knows he's crossed a line by mingling with the land humans, but how can he resist the beautiful princess whose life he saved? He must decide whether to stay on land and become like her, or continue to live without her in the depths of the ocean. 

Princess Erica can't live under the ocean, and Ari can't live above it, and yet they are destined to be together, bonded by magic. With circumstances keeping them apart and magic bringing them together, they find themselves living impossible lives with no way around it. Snatching time together here and there is one thing, but when Erica's father becomes ill and with Erica due to ascend to the throne, even that has to stop.