The Maha Kumbh Mela is in full swing. It is the largest religious gathering in the world, taking place in India across six weeks. With about 400 million people expected to join the event, authorities have spent millions of dollars to ensure the safety and security of pilgrims.

The sheer scale of the Hindu festival makes it a disaster waiting to happen. From new underwater drones to AI surveillance, here’s what’s being done to avoid deadly crushes.

The Hindu festival of Kumbh Mela, considered the largest human gathering on the planet, began in northern India on Monday with thousands of pilgrims flocking to the holy confluence of the Ganges, Yamuna and Sarasvati rivers.