en Altadefinizione. Manta rays are giant ocean wanderers, weighing up to two tons. And with the largest brain to body size of any living fish, these mesmerizingly graceful creatures are smart. They curiously interact with people, travel vast distances, and show surprisingly complex behaviour. But mantas are under threat, and this at a time when they could be key indicators of our rapidly changing world. Join Australian biologist Dr. Kathy Townsend and her PROJECT MANTA team on their journey to manta hotspots in Mexico, Micronesia, the Maldives and Australia’s Great Barrier Reef where they discover breathtaking feeding frenzies and rare mating rituals.