Eduard Rukosuev, 50, accused of rape, sexual assaults and making child pornography in case that shocks families of his underage swimmers.
The Irkutsk swimming coach who also taught in a local school has confessed to a number of the alleged crimes, say reports citing law enforcement officials.
His victims - numbering dozens and described as 'children and teenagers' - are receiving help from psychologists.
Investigators suspect up to 69 'episodes' of sexual assault, but so far charges relate to a lesser number of such assaults along with other crimes.
A Russian Investigative Committee spokesman said: "The man has been charged with 25 episodes of sexual violence, six episodes of having sex with children younger than 16, eight episodes of seducing his pupils, and 30 episodes of making pornography with minors.'
Rukosuev, a well-known and respected coach, is detained in custody until 5 January 2018.
His alleged offences cover a seven year period and a trial is now underway in Irkutsk.
'My mother told me about what he was doing after she heard it from the news,' said one boy.
'After the first news report everyone started to speak what they knew about him.
'I simply couldn't comprehend he could have done that - a man who was my swimming coach for three years, and who led Irkutsk region swimming federation.
'I did notice some strange moments in his behaviour but only realised they were weird after hearing the news.
'There were moments when he got into our changing room or even a shower room with a camera in his hands, wiping lenses. But we didn't find it weird at the time, we thought he was just taking pictures during training.'
Rukosuev's trial is closed due to the involvement of minors.
He was accused after an investigation into unrelated financial allegations.
These found 150 memory cards, DVDs and video tapes of 'completely criminal' sexual content.
The videos are alleged to show that he used his authority and influence among the families (of his swimmers) to get children involved in providing sexual services to other people.
He was described as 'wealthy', a man who enjoyed a 'luxury lifestyle'.
Famous swimming coach on trial in major paedophile probe involving dozens of children The Siberian Times 26 July 2017