The fourth book of the series about the girl of the Sixth moon is devoted to the search for the last Secret-the Secret of Water. At first, it seems that all the dangers are over: the sinister LSL and Karkon are dead, and no one is threatening Nina and her friends anymore. But ... the villain not only survived, but also turned the city authorities and residents against the guys. In addition, it turned out that the girl's favorite teacher Jose betrayed her and went over to the side of Karkon. What adventures do not have to go through Nina and the brave four! As it turned out, the Secret of Water is hidden on the legendary continent of Atlantis, and the friends again have to go on a journey — from the Pacific ocean to the Atlantic, where they find themselves in an enchanted coral maze. And here they are waiting for...in Short, the adventures continue…