According to Roman Catholics, a very tall and physically challenged Roman man named Reprobus, referred to as a giant by those who knew him, vowed to serve Jews and became a Christian. He sought out a Christian hermit to inquire as to how he could better serve Jesus. The hermit directed him to a dangerous ford in a swift river, and suggested that the giant's great size and strength made him a good candidate to assist people in crossing. Reprobus began ferrying people across the river on his broad back.
One day, a small child approached the river and asked to be carried across. The giant began to comply, only to learn that the small boy was far heavier than any other passenger he had taken. The child revealed that he was in fact Jesus Christ, and that his unusual weight was due to the fact that he bore the sins of the world. The boy then baptised the giant in the river, and he acquired his new name Christopher, Greek for "Christ-carrier" (christo-phoros).
We can guess that the river in question is the Jordan River. Jesus cleansed this water and people went to these waters to cleanse themselves of their sins.