Australia's much-hyped men's Olympic freestyle swim relay team on Friday owned up to taking sleeping medication banned by the Australian Olympic Committee and then performing "stupid" pre-Games pranks.
Members of the 4x100m freestyle relay team led by James Magnussen admitted taking Stilnox tablets at a training camp in Manchester and then making random prank calls and knocking on the doors of team mates.
"We have let ourselves down, and the people who have supported us," Magnussen, Eamon Sullivan, James Roberts, Matt Targett, Cameron McEvoy and Tommaso D'Orsogna said in a statement.
"We own up to it ... and are deeply sorry for it."
The six were dubbed the "Weapons of Mass Destruction" before the Games but failed to even make the podium in their event.
"We did take part in a bonding exercise during which members of the relay team took Stilnox... following a day of relay team bonding where we went to the movies and went to dinner," they said.
"We also acknowledge that our actions on the night were stupid."
Recreational users of Stilnox often deliberately try to stay awake, which can induce a "high" and even cause hallucinations.
The swimmers, who will now face an integrity panel, said their behaviour was childish but insisted there was "definitely nothing untoward in their actions" and none of them was drunk and they were all in bed by 10:30 pm.
They said they did not believe that Stilnox -- which is not an outlawed substance but which the Australian Olympic Committee (AOC) had recently prohibited -- had affected their performance in the pool.
Magnussen said he had been feeling "under so much pressure" and took a Stilnox tablet "to bond with these guys". Only one team member, Roberts, did not take the drug.
"In hindsight it was a ridiculous choice and ridiculous method... but I don't feel it affected my performance," Magnussen told a news conference with the five other swimmers.
The relay team failed to win a medal in London, finishing fourth behind France, the USA and Russia in an event that Australia had hoped would kick off a string of medal-winning performances in the pool.
The failure was part of a lacklustre London showing by the once-dominant Australian swimming team, which delivered its lowest tally in the pool since Barcelona 1992 -- one gold, six silver and three bronze.
It was Australian swimming's first Games without an individual gold medal since the 1976 Montreal Olympics.
The confessions follow the release of two reports into what went wrong in London that found the squad lacked leadership and that "toxic" incidents such as drunkenness and bullying had gone unchecked.
The AOC banned Stilnox more than three weeks before the Games after ex-swimmer Grant Hackett said he had developed a "heavy reliance" on the drug, marketed in North America as Ambien, while competing.
AOC secretary general Craig Phillips said it would now consider what action to take, including possible sanctions such as the withdrawal of funding in the lead-up to the Rio Olympics.
"We have in the past removed athletes from Olympic teams," Phillips said.
"We've prevented athletes from being selected on Olympic teams, because they don't measure up to our standards of behaviour," adding that it was too early to say whether this would apply to the six.