The man is described as white, 5ft 9in tall, of heavy build, balding and with tattoos on his forearms. He was wearing a black jacket, white shirt, blue jeans and white trainers. His clothes are likely to be very wet.
Hertfordshire Fire and Rescue Service carried out searches of the canal this morning. They say the water is waist deep in that location and it's possible the man was able to get out of the canal nearby and not seen by his friends because of the low visibility.