Police were called to Drift Service Reservoir near Penzance at 4pm on Thursday 18 February following reports that a body had been seen in the water.
Emergency services attended the scene and recovered the body of a man. who has been named as37-year-old Edward Hinds.
CPR was commenced by police and the ambulance service and the man was found to have sustained a suspected stab wound to his chest.
The man, now formally identified as 37-year-old Edward Hinds, was confirmed deceased at the scene.
Mr Hinds was originally from the Midlands area but had been living in the Lelant area for the last few weeks.
Senior Investigating Officer Detective Inspector Steve Hambly from the Major Crime Investigation Team said: “I am particularly keen to hear from anyone who believes they know Edward or may have had contact with him since he moved to the Lelant area of Cornwall.
“I would also like to hear from anyone who saw anything suspicious in the area of Drift Service Reservoir or Lelant during the period of Monday 15 February through till Thursday 18 February.
“Anyone with any information which may assist the investigation is asked to contact police on email@example.com quoting log 686 18 February 2021.”
A 50-year-old man arrested on suspicion of murder in connection to this death remains in police custody.