As David Berry sat down with his friends on a river bank one sunny afternoon last summer, his pre-occupations were those of many teenagers: his GCSEs and his future - in his case, as a motor mechanic.
The 16-year-old had put his phobia of water and the fact that he could not swim to the back of his mind until his moment of relaxation was shattered by the approach of two older teenagers who picked him up and said: "Berry needs a swim, let's chuck him in."
Within moments, the two attackers, both aged 17, had frog-marched their victim to the middle of the Colber Bridge on the river Stour near Shaftesbury, Dorset, and lifted David - who as a child was so afraid of water that he refused to play in the rain - over the railings.
Ignoring their terrified victim's attempts to hold on to the railings and his cries that he could not swim, the boys were seen to break David's grip and allow him to fall from the 15ft (5 metre) high bridge into the water on 9 June last year.
Firefighters retrieved his body in the evening.
Yesterday, the second of David's two killers was convicted of his manslaughter. Along with the other killer (who admitted manslaughter at an earlier hearing), the youth was found to have been 1.5 times over the drink-drive limit at the time of the attack. The 17-year-olds cannot be identified because they are juveniles.
Ian Pringle, QC, for the prosecution, said: "You had a bit to drink. It affected you a bit. You were a bit drunk, a bit louder than normal, maybe a bit of a grin on your face, and looking for what you describe as a play-fight. David didn't play-fight with you. You would from time to time grab him because you were a bully."
Jurors at Bournemouth Crown Court took two hours to convict the teenager by a unanimous verdict, after being told the boy had done "virtually nothing" to help David.
The court heard that David, who suffered from learning difficulties but had been making good progress at a mainstream school, had tried to cling to the railings, but his killers had prised his fingers away. A scene of "panic and pandemonium" ensued as classmates jumped into the river at Sturminster Newton to try to save David.
The killers, who will be sentenced tomorrow, walked home and called the police to confess their involvement in the incident, but insisted throughout that it had been horseplay. The convicted youth told the court: "When he was falling, I didn't have time to get a proper grasp and he just slipped from my hands. He slipped into the water."
David's father, John Berry, a self-employed motor mechanic who took his son out of care when he was four years old, said his son's phobia of water had been all-consuming.
Mr Berry, 40, who said justice had been served by the verdict, said: "Dave was petrified of water. He would wash his hair as little as possible. Sometimes just once a fortnight. He couldn't bear water on his face; he wouldn't play out in the rain. He wouldn't have stood out on that bridge. They didn't try to rescue him. Some people who were there said the defendant spat on the water and laughed."
Mr Berry said he believed his son, who was due to start his £245-a-week mechanics apprenticeship nine days after his death, had been bullied. "He wasn't eating. I couldn't get him to go out. He was being sick, losing weight, complaining of aches and pains. They were taking the piss out of his hair, they were calling him spotty, scabby, taking the piss out of what he was wearing."
Stephen Carrington, the headteacher of Sturminster Newton High School, which David attended, insisted there was no evidence of the teenager being bullied at school.