The 51-year-old man, from Horsforth, was discovered by passers-by floating unconscious in a stretch of the canal off Leeds and Bradford Road, Kirkstall, at about 7pm on Saturday (30th July).
He was treated by ambulance staff at the scene and then taken to Leeds General Infirmary by air ambulance where he is in a critical condition. His family have been informed.
Enquiries suggest the man had been cycling along the towpath prior to being found, although his bicycle – a brown 20-inch frame Apollo Vortice – has not been recovered.
Divers from the Force’s Underwater Search Team have searched the part of the canal where the man was found but it is possible the missing bike could be outside that area or may have been taken from the scene by someone else.
Detective Chief Inspector Simon Bottomley, of the Homicide and Major Enquiry Team, said: “There could be a number explanations as to how this man came to be in the canal and we are keeping an open mind at this time. It may have been an accident or he may have been the victim of an assault.”
“I am keen to hear from anyone who has seen this man cycling along the towpath in this area around 7pm or who has any information about the whereabouts of his brown Apollo Vortice mountain bike.”
The injured man is described as white, young looking 51 year old, 6ft 2, 14 stone stocky build, brown short hair, tanned complexion and clean shaven. He was wearing a bright orange / red T-shirt, black shorts, white trainers and grey fingerless cycling gloves.
Anyone who saw the man cycling on the towpath or who has any information that could assist the investigation is asked to contact detectives on 01924 334692.