Essex Police have reiterated that the investigation into the death of Stuart Lubbock remains open.
Mr Lubbock, who was 31, was found in the swimming pool of a property, belonging to Michael Barrymore in Roydon, near Harlow on March 31 2001.
The Father-of-two from Harlow was taken to hospital where he sadly later died. Mr Lubbock had suffered multiple injuries and his death remains unexplained.
The appeal comes as Mr Barrymore is due to appear on ITV tonight in an episode of Piers Morgan's Life Stories.
In the show the former Game Show host tells Piers that "couldn't be more sorry" for his behaviour on the night Mr Lubbock died.
Barrymore, now 67, said he remains "100% innocent".
He said he deserved to "walk around with my head held high for the rest of my life" after winning compensation from Essex Police last year for wrongful arrest.
Assistant Chief Constable Tim Smith, head of the Kent and Essex Serious Crime Directorate said: “The investigation into Stuart’s death, and how he sustained such serious injuries is still open.”
“We owe it to him and to his family to piece together exactly what happened in the swimming pool at Mr Barrymore’s home in March 2001.” Although it has been 18-years since Stuart’s tragic death, the pain of his loss and not really knowing what happened to him is no less painful for his father and family – they still want and need answers. The passing of time can mean that loyalties change and we would urge anyone who now wishes to come forward to us with information about Stuart’s death, to do so – it’s never too late to do the right thing."
Anyone with information can contact Essex Police on 101 or Crimestoppers anonymously on 0800 555 111.