Hundreds of Hindus worshipped in the heavily polluted Yamuna river on Wednesday to celebrate the ancient festival of Chhath Puja in New Delhi.
A vast stretch of the river is covered with white toxic foam, caused partly by pollutants discharged from industries ringing India's capital.
Despite this, devotees stood knee-deep in its frothy, toxic waters, sometimes even immersing themselves for a holy dip to mark the festival.
The 1,376-kilometre (855-mile) Yamuna is one of India's holiest rivers to Hindus. It is also among the most polluted in the world.
Over the years it has become dirtier as most of the capital's sewage, farm pesticides from neighbourhood states and industrial effluents from factory towns flow into the waterway despite laws against polluting.
In a city that already has the world's most polluted air, a dangerously unhealthy waterway is a concern for many. Yet, devotees flock to it every year during the festival.
India's capital, home to more than 20 million people, is one of the world's most polluted cities.
Winters have particularly become a time of health woes, when the city is covered with a toxic haze that obscures the sky and blocks sunlight and air pollution levels reach catastrophic levels.
Pollution levels soar as farmers in neighbouring agricultural regions set fires to clear their land after harvests and prepare for the next crop season.
On Wednesday New Delhi's air quality index remained in the category of "very poor," according to SAFAR, India's main environment monitoring agency.