Two men have been jailed for manslaughter over a fatal assault filmed on a mobile phone.
Jonathon Lawson of Milton Keynes and Sydney Quirke from Southend
Mark Watts from Pitsea in Essex died in March last year after being pushed into cold water at Lakeside shopping centre.
The 44-year-old had learning difficulties, with an estimated mental age of 10.
At Chelmsford Crown Court, Jonathan Lawson, 20, of Milton Keynes, was given 14 months jail and Sydney Quirke, 18, from Southend, 12 months.
Lawson was convicted of manslaughter after a trial and Quirke admitted the charges at an earlier hearing.
A 17-year-old youth from Grays, who cannot be named, was acquitted of the same charge.
The court heard Mr Watts, who lived in sheltered accommodation, was sitting naked on a jetty dangling his feet into the lake when he was killed.
Mr Watts, who could not swim, had undressed after drinking at a nearby pub.
The attack - which was also caught on CCTV cameras - was filmed by one of the youths on a mobile phone as the man drowned in what was described in court as a "happy slapping" prank.
Some family members were angered by the sentences.
Mr Watts' aunt, Rita Bonar said after the hearing: "I thought the sentence was terrible. You get worse if you don't pay your poll tax.
"I cannot forgive them for taking away our beautiful boy from us in such a tragic manner.
"I hope youngsters who think happy slapping is funny learn from this. But I don't suppose they will.
"This was a case where the worst happened. The sentence should have been a lot longer."
Deputy High Court Judge John Blofeld told the two men: "It was more than just a foolish prank. It was a criminal act and it had devastating consequences.
"He met his death at your hands and you will have to live with that for the rest of your lives."