The Pirate’s Princess by Bethany Wicker

Sera just wants to belong…. now, she must find a way to rule.
When Sera discovers that her dad is not only alive, but also the siren king, she finds herself thrown into the middle of siren politics. She must prepare to become queen. But the mermaids have taken something valuable from the sirens: a necklace that gives them their full power. According to siren lore, only the Fated Princess can retrieve the necklace.
Sera knows what she needs to do, but try telling that to her heart. It yearns for Steel, and she fears she’ll never see him again. How can she learn to rule the sirens when her heart is with a certain captain?