More than 20 Chinese cockle pickers died in Morecambe Bay because of the "gross negligence" of their gangmaster, Preston Crown Court has been told.
At the start of the trial of five defendants, the jury was told the cocklers, all illegal immigrants, drowned because Lin Liang Ren's failure to look after them.
The victims were part of a team caught by the incoming tide off Hest Bank on February 5 last year.
Tim Holroyde QC, prosecuting, told the jury of nine women and three men: "Some managed to swim to safety or were rescued, but at least 21 drowned.
"It is the prosecution case that their deaths were caused by the criminal negligence of Lin Liang Ren.
"He was controlling the cockle pickers. He was responsible for them and completely failed to take proper care for their safety as they worked in the cold and dark.
"He is charged with manslaughter by gross negligence of each of the 21 cockle pickers known to have drowned."
Ren, 29, from Liverpool, denies the charges. He also denies perverting the course of justice and conspiracy to facilitate illegal immigration.
Ren's girlfriend, Zhao Xiao Qing, 20, from Liverpool, denies perverting the course of justice and facilitation.
Lin Mu Yong, 31, from Liverpool, denies facilitation.
David Anthony Eden, 62, from Irby, Wirral, and his son, David Anthony Eden Jnr, 34, from Prenton, Wirral, also deny facilitation.
Mr Holroyde said Ren and his girlfriend Zhao tried to cover up his actions.
He said: "No doubt because he was well aware of his responsibility, Ren immediately set about trying to distance himself from the tragedy.
"He tried to leave the scene. When police asked him what happened, he used a different name and gave an untruthful account of his movements.
"He instructed the Chinese survivors they must not tell anyone he was the boss, and instead say the men in charge were Lin Li Shui and Tian Long. Both had drowned."
The court was told the team of Chinese cocklers were helped to stay in the country by the defendants.
Mr Holroyde said: "They had managed to enter this country without being caught or been granted limited permission to stay and had then breached the conditions .
"They were not entitled to work, but as cockle pickers could earn an income and were provided with some form of accommodation and basic food.
"It is the prosecution case that all five of the defendants played a part in assisting them."
The court was told Lin Liang Ren and Lin Mu Yong were gangmasters.
Lin Mu Yong's workers were based in Morecambe, Lin Liang Ren's were based.
Mr Holroyde told the jurors they would be hearing from a number of witnesses, including Lin Guo, who worked for Lin Liang Ren.
He said: "He describes how Lin Liang Ren worked for, and sold cockles to, a succession of English bosses.
"The first of these was known to Lin Guo as Wayne, the second as Michael. After them, says Lin Guo, came a third English boss, Tony. That was Tony Eden."
The court was told that, in August 2003, Lin Mu Yong began renting a second property, in Morecambe, and said he intended six or eight Chinese people to live there.
Mr Holroyde said: "Yong used the terraced house for cockle pickers during the summer and autumn of 2003.
"On an occasion, in the autumn, when the landlord's agent visited, he found at least 30 mattresses but no other furniture.
"The conditions were severely overcrowded, to the extent that the local authority served a notice to end the tenancy.
"The landlord obtained an order for possession in early January 2004 The Chinese occupants stayed on, but disappeared after the tragedy, leaving about 20 mattresses behind."
In September 2003, Ren rented a second house in Liverpool and Chinese people started to move in.
The court was told Kwek Chee Seng, who had worked for Lin Liang Ren, warned him of the dangers of that area of Morecambe Bay.
Mr Holroyde said: "From the outset, Ren knew of the risks for workers in that area."
The trial, before Mr Justice Richard Henriques QC, is due to last between four and six months.