A pool of deathly blue

"Twins Madison and Mason Page have everything two kids could ever want, but they don't seem to appreciate any of it. One day, they dive into their luxuruous swimming pool and surface in a ver different place--another town, long since abandoned. Trapped in this new world, they venture forth, finding evidence that the town's former residents must have suffered some sort of horrible fate before disappearing. then it hits them--they've been trasported to the ghost town of Pripyat, which has stood empty since the local power station exploded many yearsr earlier, a nuclear plant known as Chernobly"--Back cover.