The Water Witch by Jessica Thorne

Sitting side by side on the clifftop, he turns to her solemnly and says, ‘The water witch is real.’ She rolls her eyes and grins, teasing him. ‘Sure. A psycho mermaid. Got it.’ But now he’s gone forever… will she find the truth beneath the waves?
Brittany, France. Ariadne Walker’s fiancé Simon drowned in the stormy Atlantic Ocean doing what he loved: searching for the lost underwater city of Ys. Local legend says it was destroyed centuries ago when the princess of Ys became a water witch, cursing the name of the man who betrayed her.
Ari never believed these tall tales. And the letter Simon sent before he died finishing their relationship is a devastating secret she’ll take to the grave. But arriving in Brittany, Ari encounters a man emerging from the sea in a rocky cove, saltwater dripping from his dark hair. Rafael swears the legends are true: and his ancestor was cursed by the water witch. Now, his own life is in terrible danger. And the secret to breaking the curse lies hidden in the lost city.
When Ari finds a strange engraved mask on the sea bed, and a cryptic map amongst Simon’s things, she has no choice but to believe Rafael’s plea. Can they follow the trail and save Rafael’s life? Poring over the map by candlelight, the flickering flames only add to the heat between them… but will Ari’s fragile heart soon be shattered all over again? And will they ever find Ys and break the curse – or will the water witch demand another sacrifice?