The Mermaid's Tale - Chronicles of the Undersea Realm, #1

A Tail Could Tell a Tale Locklyn Adair has never fit in. The legs she inherited as a result of her great-great-grandmother's curse make it impossible for her to belong under the sea. When her niece is also born without a tail, Locklyn is determined to save her from similar rejection by sending her to the only place in the Undersea Realm where legs are acceptable-the Lost Island of Atlantis. Darin Aalto would do anything to protect his family, even spearheading an impossible quest to find treasure that has been lost for over a hundred years.
But when his best friend, Locklyn, joins his crew, his ability to keep her safe-and his shot at winning her heart-comes perilously close to being swept away. A family curse, lost treasure, unrequited love, and a race against time intertwine as Locklyn and Darin seek to save their family, their kingdom, and eventually the entire Undersea Realm without losing each other.