Two teenagers convicted of murdering sixth-former Ben Bellamy on a Swansea beach have been jailed for at least 22 and 18 years.
Joel Taylor, 18, - who had the longer sentence - and Joshua Thomas, 16, were given life for robbing and beating Ben, 17, and leaving him to drown.
They were convicted at Swansea Crown Court jury of killing Ben in September.
Andrew Rafferty, 18, who was cleared of murder but convicted of manslaughter, will serve a minimum of five years.
After the sentence, Ben's mother said she woke up some mornings imagining she had had "a terrible nightmare," before realising "my wonderful Ben has gone".
"I have often found myself shopping and if I have seen something that Ben would have liked, or things he already had, I have literally put my shopping down and fled home in tears," she said.
But she added: "I don't want people to feel sorry for me because I am still here. It is Ben I want people to feel sorry for.
"He was the most wonderful, caring, sensitive person. He was so intelligent and could have achieved anything he wanted in life because he had the ambition and ability to achieve."
Judge Justice Roderick Evans told Taylor and Thomas they had committed an "act of cold-blooded and calculated evil of a kind it is difficult to comprehend."
Joel Taylor (left) and Joshua Thomas were convicted of murder
"You took Ben Bellamy out into the sea to a depth of one metre and you drowned him. It was a determined cold killing."
He said: "On the evidence before the court Ben Bellamy was a decent, popular and academically able 17-year-old.
"He had a promising life ahead of him until he met the three of you. His killing has profoundly affected this city."
Det Supt Ken Isaac said nothing could bring back Ben, but justice had been served.
"We will continue supporting Ben's family with a trained family liaison officer to help them dealing with this difficult time," said Det Supt Isaac.
Andrew Rafferty was found guilty of manslaughter
He praised Swansea people for showing a "great deal of support and dignity throughout this difficult time and have been extremely valuable in their assistance in the investigation".
Ben, from Sketty Park, Swansea, was walking home after a night out in Cinderella's club in Mumbles when he started talking to the trio and was invited to walk with them.
He was later dragged onto the beach and attacked by all three.
Rafferty used his elbow to keep him on the ground, with the other two kicked and stamped on his head and body.
Rafferty, who left the beach during the attack to try to use Ben's cash card, was found guilty of manslaughter.
Thomas was also found guilty of robbery at the five-week trial, while his two co-defendants had already admitted robbing Ben.
None of the three gave evidence at their trial.
They had been due to be sentenced on 28 April, but the judge said it would not be proper for him to do so because of inadequacies in reports on Taylor and Rafferty.
The hearing was adjourned so that all three defendants could be sentenced together.
Ninety officers were involved in the murder investigation.
More than 400 hours of CCTV footage was viewed during the inquiry and 600 statements were taken.
Dee Langley, 23, who disposed of evidence in the case, was jailed for two-and-a-half years. A cousin of Joel Taylor, she admitted attempting to pervert the course of justice by disposing of Ben's mobile phone and silver neck chain, and a blood-stained T-shirt worn by Joshua Thomas.