Wil Mara 
Pool of Deathly Blue [PDF ebook] 

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 luxurious swimming pool and surface in a very different place. They emerge into 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 have somehow been transported to the ghost town of Pripyat, which has stood empty since the local power station exploded many years earlier, a nuclear plant known as Chernobyl.