In Project Manta, the fourth in the Wild Ones wildlife documentaries series, we meet the Manta ray, one of the largest of all marine animals, and yet one of the oceans' best kept secrets. Weighing up to two tons, these mesmerising creatures glide through the oceans like giant shadows. Manta rays aren't just giant ocean wanderers, they're smart. With the largest brain to body size of any living fish, these mesmerizingly graceful creatures are intelligent. They curiously interact with people, travel vast distances, and show surprisingly complex behaviour. Join Australian biologist Dr Kathy Townsend and her Project Manta team as they reveal the mantas' secret world. Filming takes place in manta hotspots in Mexico, Micronesia, the Maldives and Australia's Great Barrier Reef where they discover breathtaking feeding frenzies, and rare mating rituals. But mantas are under threat and this at a time when they could be key indicators of our rapidly changing world.