The incident happened at the weir near the pontoon at Glasgow Nautical College, in the city centre.
The man's boat had crashed into the weir gates as he tried to sail through at around 10.30pm on Sunday.
Glasgow river hero George Parsonage, and his 17-year-old son, Ben, rescued the man and helped him out of the water.
The incident has seen Mr Parsonage, of Glasgow Humane Society, repeat his call to only allow boats to pass through the weir during daylight hours.
He said: "If these gates got damaged, there would be serious consequences - the banks could collapse.
"I'm very proud of what happened, and how my son and I managed to help the man to safety."