Gargantuan prehistoric sharks, aquatic civilizations, and a sinister centenarian...

It's been twelve years since Lou Melville was deep in the ocean observing megalodons with her mother and billionaire Wolfgang Feiersinger. Now, all grown up and the heiress to his fortune, Lou gets sucked back into his depraved world of legends and monsters and decides to lead a dangerous expedition to the ruins of an ancient underwater city where she may uncover the mystery behind her own origins.