Rescue Sirens : The Search for the AtavistJessica Steele-Sanders et Chris Sanders2015

For Nim, lifeguarding is more than just a summer job. She and her friends are Rescue Sirens, mermaids sworn to an ancient vow to watch over and protect humans -- and the best way to do that in today's world is by hiding in plain sight as lifeguards. When the Rescue Sirens receive word that a special human -- unwittingly possessing the rare power to turn into a mermaid -- has made her way to Miami Beach, it's up to them to find her before she transforms on her own and she's either discovered... or lost forever.