Naked Hindu ascetics and pilgrims are taking holy dips in sacred rivers in the first major bathing day of the Maha Kumbh festival, which is the largest religious congregation on Earth.

For pilgrims at the largest gathering of humanity, ritual bathing in India's holy rivers includes a key challenge -- finding your family and clothes after the chilly dip. But many said that the effort to bathe in the holy waters was worth it.

The Maha Kumbh festival — held every 12 years — started Monday, with more than 15 million pilgrims bathing in the holy rivers, according to officials.