Sevenwaters, book 5: Seer of SevenwatersJuliet Marillier2010

The young seer Sibeal is visiting an island of elite warriors, prior to making her final pledge as a druid. It's there she finds Felix, a survivor of a Viking shipwreck, who's lost his memory. The scholarly Felix and Sibeal form a natural bond. He could even be her soul mate, but Sibeal's vocation is her true calling, and her heart must answer.

As Felix fully regains his memory, Sibeal has a runic divination showing her that Felix must go on a perilous mission-and that she will join him. The rough waters and the sea creatures they will face are no match for Sibeal's own inner turmoil. She must choose between the two things that tug at her soul-her spirituality and a chance at love...