The Jordan River and the Sea of Galilee are the closest things Christianity has to holy bodies of water. The Jordan River was the sight of several Old Testament miracles including Elisha ordering Naaman to bath in the Jordan so that Naaman would be cured of leprosy (2 Kings 5:14). The Jordan River plays a large role in the New Testament as the place where John the Baptist preaches and Jesus is baptized (Matthew 3). The Sea of Galilee, the lowest freshwater lake in the world with its surface 686 feet (209 meters) below sea level, is the sight of several miracles including Jesus' walking on water (John 6:19) and Jesus feeding the masses (Mathew 14: 16-20).
The Catechism of the Catholic Church ties water well into the Rite of Baptism. Water in this ritual represents the word of God, Christ’s death and rebirth, a purifier of sins, and the source of life. Catholic, Orthodox, and most Protestants require water baptisms, of "living water" i.e. fresh, because of the importance assigned to water.
The Ganges River is the major holy river in Hinduism. While holy tradition or divine acts make mundane bodies of water holy in other traditions, Hindus believe the Ganges River itself is divine. Most Hindu traditions hold that the river is the goddess Ganges. Hindus believe that water from the Ganges can wash away sins and free one from the cycle of reincarnation. Having one's ashes released into the river is seen as being completely absorbed into the goddess and heaven. There are also six other major rivers viewed as holy in Hinduism: the Yamuna, Godavari, Sarasvati, Narmada, Sindhu, and Kaveri Rivers.
Fresh water plays a major role in Hindus' daily lives. From a morning cleansing ritual to having funeral grounds next to rivers, fresh water is a must for Hindus.
On fresh water traditions within modern Judaism, whether global or local, I must admit my ignorance. However, a well trusted a graduate student in Jewish studies (and reader of this geography blog!) gave me some insight. While there is no globally-viewed holy body of water, water is used as a purifier in the mikveh bath. The rabbi states, "the mikveh is used for purposes of ritual purity, including for the use by women following menstruation. It is used for important lifecycle events in the life of men and women and is an important component in the conversion process. There must be a natural water source (living water) for the mikveh - from rainwater, a flowing stream, or from snow for a mikveh to be valid. The rituals can also take place in a living body of water like a river or the ocean."