A court in the southern German state of Baden-Württemberg has sentenced a 34-year-old swim teacher to 12 years in prison for sexually assaulting 37 girls during swim lessons over a two-year period.

The man had pleaded guilty early in the trial to attacking the girls in swimming pools and in changing rooms throughout the state from 2015 to 2017. The victims were between 4 and 12 years old. He threatened some of them with violence to stop them from telling their parents about the attacks.

"I'm ashamed of what I've done," he said after pleading guilty, reported the Stuttgarter Zeitung newspaper.

In total, he was charged with more than 200 counts of sexual assault, including multiple counts of physical assault and the production of child pornography, against 40 girls. Cases involving three of the girls were dropped after police were unable to identify them.

Read more: What do Europeans consider sexual harassment?

During the trial, prosecutors used recordings of some of the attacks that he had filmed with an underwater camera as evidence. Some of the parental witnesses said he did not fill the girls' flotation aids with air, so that he could assault them while he kept them afloat, the Stuttgarter Zeitung reported.

The man had initially accused another man of extortion and coercing him to commit the crimes, but the court quickly dismissed those accusations after an investigation found no evidence.

Police arrested the man in September 2017 after parents of two of the girls had separately accused him of sexual assault.

Read more: Half of women in Germany victim of sexual harassment, survey

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