Olivia Brophie and The Pearl of Tagelus by Christopher Tozier
Young Olivia moves to the Florida scrub and finds much more than sand and scrawny oak trees. Caught in a battle for the fate of the universe, she slips down a tortoise burrow into the vast Floridan Aquifer where ancient animals thrive in a mysterious world. She learns the secret of a brilliant pearl and must use its power to discover her life’s ultimate destiny. this is the first novel in the Olivia Brophie series.