A man arrested on suspicion of murder after a body was found in the River Thames has been bailed.
The victim, who was thought to have been fishing before he disappeared, was discovered in the water in Walton-on-Thames on Thursday.
A post-mortem examination on Friday determined the man, who was in his 40s, was killed as a result of trauma to the head, Surrey Police said.
A 25-year-old man questioned in connection with the death on Friday evening has been bailed until September 29.
The Surrey Fire and Rescue Service had conducted the search of the river after concerns were raised about the missing man's safety. His remains were found at around 4.45pm.
He is yet to be formally identified.
Senior investigating officer, Detective Superintendent Adam Hibbert, said: "This was an appalling incident where the victim sustained significant, and ultimately fatal, head injuries.
"A detailed and extensive investigation is continuing to establish the circumstances surrounding the incident and we are determined to bring those responsible to justice.
"The area is popular with fisherman and dog walkers and I would urge anyone who was in the area on Thursday and may have seen or heard anything out of the ordinary to contact Surrey Police as a matter of urgency.
"Our thoughts remain with the man's family at this extremely difficult time and on their behalf we are continuing to ask that their privacy is respected."