Police are investigating the death of a man whose body was discovered in the Leeds-Liverpool canal.
Jan "Jon" Swindlehurst, 61, was found dead in a stretch of the canal off Wyther Lane, Leeds, on Saturday.
A man was seen wading in the water at the same time, but left the scene, at about 1330 GMT.
Police are asking for information from anyone who saw Mr Swindlehurst driving his mobility scooter along the canal or the other man seen in the water.
It is thought Mr Swindlehurst, who was married and suffered from health problems, left his home in Armley around midday to go to the Morrisons store in Kirkstall on his mobility scooter.
Witnesses reported seeing another man wading in the canal at the scene, who then got out of the water and walked in the direction of the city centre.
"It may well be that he had been trying to rescue him and he may have seen... how Mr Swindlehurst came to be in the water," said Det Ch Insp Mark Ridley of West Yorkshire Police.
Describing him as white, 6ft tall and slim with dark hair and a thin face, he appealed for the man, or anyone who knows him, to come forward.