The Siren by Kiera Cass

Kahlen was supposed to drown on that sinking ship, but instead the Ocean and Her Sirens rescued her. Committed to one hundred immortal years of singing songs to provide human sacrifices for the Ocean to live, Kahlen is the most obedient siren the Ocean has, until she accidentally meets Akinli, a human. Torn between friends, family, and her new love, Kahlen has to make difficult choices to survive her sentence as a Siren.