Return to the subsea frontier with Ty and Gemma, where the mysteries of the deep are deadlier than ever. With time running out for his parents, Ty's desperation leads the two teenagers to the underwater underworld...and into an alliance with the outlaws of the Seablite Gang. But one mystery soon leads to another. How has an entire township disappeared? Why is the local sea-life suddenly so aggressive? And can the Seablite Gang be trusted...or are Ty and Gemma in deeper water than they realise?