Poland have sent six swimmers home from the Tokyo Olympics after selecting too many by mistake.
Poland initially picked 23 athletes but had to cut that to 17 based on world governing body FINA's qualifying rules.
Polish Swimming Federation (PZP) president Pawel Slominski has apologised and said he understood the anger of those who have returned home.
"I express great regret, sadness and bitterness about the situation," he said in a statement.
"Such a situation should not take place, and the reaction of the swimmers, their emotions, the attack on the Polish Swimming Federation is understandable to me and justified."
Slominski added the error was due to the "desire to allow as many players and coaches as possible to take part in the Games".
One of the six athletes Alicja Tchorz, who represented Poland at the 2012 and 2016 Olympics, expressed her anger at the mistake on social media.
"Imagine dedicating five years of your life and striving for another start at the most important sporting event, giving up your private life and work, sacrificing your family and your dedication results in a total flop," she wrote on Facebook.
Another of the six, Mateusz Chowaniec, said on Instagram: "I'm deeply shocked by what happened. This is an absurd situation for me that should never have happened. In fact, I hope to wake up from this nightmare eventually."
The majority of the Poland swimming team have signed an open letter to the PZP calling for the board to resign over the incident.