A swim coach was arrested on suspicion of committing an alleged sexual offence against children in the sport.
The man, in his 30s, was arrested on Tuesday, and later released without charge.
A Garda spokesman said the man was arrested on suspicion of alleged offences contrary to the Criminal Law (Sexual Offences) Act.
The coach was suspended by the swimming governing body after an allegation of inappropriate behaviour was made earlier this year by a whistleblower, who was part of the group of swimmers.
It is believed that the allegation related to concerns about a recording device or devices used in the building in which the swimmers were training. The male coach had been teaching underage swimmers in a Dublin pool.
After becoming aware of the concerns Swim Ireland reported the matter to gardaí, at which point an investigation was opened by specialist detectives, a Garda source said.
He was detained and questioned at a garda station in west Dublin but later released without charge.
A file will be prepared for the Director of Public Prosecutions.
"As this is an ongoing criminal investigation An Garda Síochána has no further comment," the spokesman added.
In a statement on Thursday, Swim Ireland said the matter was raised with its National Children’s Officer earlier this year, who in line with its procedures, contacted the statutory authorities straight away.
“The matter is now being investigated by Gardaí, and a coach has been suspended. All relevant protocols are active including informing and assisting relevant parties,” the statement said.
“Our priority is to offer appropriate support to those involved and to co-operate with the Garda investigation.
“As we understand it this is not a matter that has previously been raised with the Gardaí and our National Children’s Officer continues to liaise closely with them.