They have issued a third appeal in the hope of naming him and thanked members of the public who have already got in touch.
The man, who was in his 50s, was 5ft 8in tall, clean-shaven, with brown hair that was greying at the sides.
Police said he died alone, but not in suspicious circumstances.
Detective Inspector Richard Thornton said: "We would continue to appeal for the public's help and ask anyone who believes they can help police identify this gentleman, or if you have information that could help with our inquiries".
Supt Melanie Jones said that police wanted to "reunite him with his friends, with his family, so he can be put to rest in dignity".
"We have had a team of detectives working on this since the body was found on Friday, but unfortunately we have no further leads on who this man is," she added.
The man was wearing blue jeans (with a black belt and silver buckle), a black t-shirt and black and silver training shoes.
He also had an appendix scar on his body and two compression bandages on his left, upper arm
The only personal item in his possession when he was found was a house door key.
Police said that early indications were that the man had been in the water between 24 and 48 hours.
Police have still not identified the body of a man discovered in water near Shaw's Bridge in south Belfast on Friday afternoon.