After receiving the task of looking for a book, I found the wreckage of a helicopter at Tianya Beach, and a Naga can be found at the bottom of the sea nearby. This game is called Mermaid. In the shallow sea near the south of the plane. Just look carefully. When you find it, you will receive a task to deliver a letter to Nalian, and then come back to find her after delivery. She will give you a BUFF with a swimming speed of 500% and let you swim directly south to the island.