Water

Swimming on Mars? Not likely. There is water on Mars, but it is frozen solid beneath the surface. In the future, not long from now, that ice will prove invaluable for those that live there. It will provide not just their water for drinking and growing crops, but also their air, their fuel, and their economic ties with Earth. And in this book it will provide a terrifying experience and a grueling fight for survival for sisters Cas and Ori and their classmates.

Cas and Ori are among the first children born on Mars. The Generation Mars series follows their adventures as they grow up in an environment unlike any in which children have grown up before. Each book in the series uses a fundamental element of survival as title and jumping off point: Air, Shelter, Water, Food.
In book three, Water, the children are touring an abandoned ice mine from the colony's early years when an unpredictable seismic event traps them in a dark and shifting labyrinth of ice. Escape will require resilience and sacrifice beyond anything they have experienced.