It has actually been seen that anyone who regularly worships mother Ganges simply by bathing in her water keeps very good health and gradually becomes a devotee of the Lord. This is the effect of bathing in the water of the Ganges. Bathing in the Ganges is recommended in all Vedic shastras, and one who takes to this path will certainly be completely freed from all sinful reactions. The practical example of this is that the sons of Maharaja Sagara went to the heavenly planets when water from the Ganges merely touched the ashes of their burnt bodies.
Source: A.C. Bhaktivedanta Swami Prabhupada (2014 edition), “Srimad Bhagavatam”, Ninth Canto, Chapter 9 – Text 14