Call of the Sea by Michelle M Pillow - Paid

Ian O'Connell, heir prince to his clan, has no plans to settle down even though his untamed nature keeps him on the prowl for female company. The only woman he could ever want saved him from a watery grave before disappearing from his life forever. But that was a long time ago, too long for a mortal woman to have survived. Though he searched for her, in the end it was in vain.

Cursed by the power of the Cancerian crab, Ceana is doomed to spend her eternity in the ocean as a mermaid. Her only reprise is on a full moon, when she becomes human and must find shore. Centuries have passed and she's all but given up on the one who could save her. Brief passion is all she has and she's willing to take what she can get especially if it's with an intriguing lycan who's untamed nature just might be her salvation.