It's the newest, most thrilling sightseeing cruise in the Alien Safari brochure.

For ranger Jan Corbija, ferrying rich tourists around the aquatic wonders of Hesperidia's islands helps to fund her important scientific research. But her final 'White Water' tour of the season might just be one sail too many when passengers steal her equipment for a dive into uncharted depths, triggering a tragic series of events.

A leisurely cruise becomes a race against time when a young girl is swept overboard during a storm, and Jan's beloved dog, Stopper, jumps in to rescue her. Jan will stop at nothing to find them, even if it means risking the safety of everyone on board. As the deep-sea salvage operation grows into an invasion force, she must contend with hostile humans and alien creatures alike in her quest to retrieve her brave canine companion and the girl in his charge.

Help arrives in the shape of her famous detective boyfriend, Ferrix Vaughn, who's left a crucial bombing investigation to come to her aid. But he soon realizes something unprecedented has been lost on Hesperidia. A secret from long ago. A secret that could change the course of human history.

It's past the point of no return for adventure and excitement in this white-knuckle sequel to the acclaimed Alien Safari.