Scilly's former Police Sergeant Colin Taylor has been criticised for his handling of the death of Josh Clayton, according to the BBC.
The 23-year-old's body was found on rocks off Tean on September 23, 2015, ten days after he went missing following a party on Tresco.
Two professional standards reports - one by Devon & Cornwall Police and one by Dorset Police - identified problems with how the investigation was conducted.
The first report upheld 22 of the Clayton family’s complaints about the probe, and partially upheld two more.
One of six learning points identified for Sgt Taylor, who left the islands in August 2016, described his use of a "water diviner" during the search for Josh as "not appropriate".
He was also criticised for confronting the Clayton family while they were eating dinner in a pub after they raised questions over his methods - behaviour he should have known was "just not appropriate".
While acknowledging that there was no doubt that he tried to put the family at ease, the report accused him of displaying "poor judgement" in his conversations with them, with some of what he said described as "insensitive through its banality".
He was also found to have failed to secure Josh's room, despite it being "fair to expect that all potential evidence should be secured and preserved".
Six learning points were identified for senior investigating officer Detective Inspector Debbie Jago and four for Devon & Cornwall Police.
The force said it would apologise to the family.
Josh's mum Tracey Clayton said she wanted police to compensate her family for the anguish they had suffered and wished to recoup some of the £70,000 spent on legal fees and private investigation, according to the BBC report.
She said she would like to spend any other money to start a charity in her son's name, helping people who found themselves in a similar situation.
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