Terra (Book Two of the Elements Series) by Tracy Korn
Under Pressure, Under Fire…Some Will Rise, and Some Will Fall.
Getting out of Gaia Sur was almost as hard as getting in, but there’s no going back now. Jazwyn Ripley and her friends have no choice but to venture into the caves and tunnels underneath the ocean floor as the messages they’ve been receiving get stronger. Tensions rise and loyalties are tested when another of their crew is captured, and one critical choice means following unlikely allies down a path most would never dare—across the seven biomes of “The Rush”—which, if they survive, will either lead to freedom or imprison them forever.