A dip in the Ganges is, generally speaking, synonymous with the idea of purification.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/west-bengal-rivers-are-not-fit-even-bathing-says-report-0
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/hindu-new-delhi
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/west-bengal
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/river-pollution
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/west-bengal-pollution-control-board
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/central-pollution-control-board-cpcb
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/ganga
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/mahananda
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/damodar
[10] http://admin.indiaenvironmentportal.org.in/category/thesaurus/murshidabad