The earliest report of a monster in the vicinity of Loch Ness appears in the Life of St. Columba by Adomnán, written in the sixth century AD (year 565). According to Adomnán, writing about a century after the events described, Irish monk Saint Columba was staying in the land of the Picts with his companions when he encountered local residents burying a man by the River Ness. They explained that the man was swimming in the river when he was attacked by a "water beast" which mauled him and dragged him underwater. Although they tried to rescue him in a boat, he was dead. Columba sent a follower, Luigne moccu Min, to swim across the river. The beast approached him, but Columba made the sign of the cross and said: "Go no further. Do not touch the man. Go back at once." The creature stopped as if it had been "pulled back with ropes" and fled, and Columba's men and the Picts gave thanks for what they perceived as a miracle.
Believers in the monster point to this story, set in the River Ness rather than the loch itself, as evidence for the creature's existence as early as the sixth century. Sceptics question the narrative's reliability, noting that water-beast stories were extremely common in medieval hagiographies and Adomnán's tale probably recycles a common motif attached to a local landmark. According to sceptics, Adomnán's story may be independent of the modern Loch Ness Monster legend and became attached to it by believers seeking to bolster their claims. According to R. Binns, this account is the most credible of the early sightings of the monster; all other claims before 1933 are dubious and do not prove a tradition of sightings before that date.