The body of Dylan Cecil, a four-year-old boy who slipped from a jetty, is believed to have been washed out to sea after specialist sonar equipment failed to find him, experts have said.
Dylan, from Northamptonshire, was on holiday with his family when he stumbled into the muddy water at Burnham-on-Sea, Somerset, on Sunday.
Volunteers from the UK underwater rescue organisation SARbot used specialist sonar equipment to scour the water for Dylan's body but after spending hours on the water his body could not be found.
The organisation was using sonar equipment which is more sensitive than that used by police and had earlier said that if the youngster's body was still in the area, they would find it.
Duncan Winsbury, chief executive of SARbot, confirmed the search had been brought to an end. "We've just completed the search and have searched the whole bay and we've not found anything," he said. "We believe that the currents may have taken him right out to sea now, he's certainly not in the bay."
Dylan, from Kettering, Northamptonshire, was visiting his grandparents with his mother Rachel McCollum, father Darren Cecil and two younger sisters, aged one and three.
He had wanted to get a closer look at the sea when he slipped off the side of the jetty and disappeared beneath the water. His parents desperately tried to rescue him, but were unable to reach their son and had to be pulled from the water by passers-by.
Dylan's mother said he fell into a "whirlpool" and she knew immediately that she would not see him again despite her desperate efforts to save him.
The Coastguard and police launched a large search and rescue operation after a member of the public saw Dylan's parents attempting to rescue him. The search for Dylan, who was wearing a T-shirt and shorts, was called off on Monday afternoon but volunteers have continued to look for him in order to bring closure to his family.
The SARbot UK team, based in Weymouth, Dorset, were using side-scan sonars designed to detect human remains underwater. Four volunteers from the charity started their search on Wednesday morning, scanning an area off the beach, and later concentrated on a five-mile channel where they believed Dylan's body may have been located.
The Cecil family were put through further trauma after someone took to Facebook posing as their missing child. The comments, which were later removed from the website, were mockingly written 'from heaven'.