NEW DELHI - One of India's most sacred rivers appears to be coated with a thick layer of snow. Except it isn't.A vast stretch of the Yamuna river is covered with white toxic foam, caused in part by pollutants discharged from industries ringing New Delhi.Still, on Wednesday hundreds of Hindu devotees stood knee-deep in its frothy, toxic waters, sometimes even immersing themselves for a holy dip to mark the festival of Chhath Puja.The 1,376-kilometer (855-mile) Yamuna is one of the holiest rivers for Hindus.