Peter Sharp has quit as coach of NRL club Cronulla, effective immediately.
Chief executive Steve Noyce accepted Sharp's resignation late on Monday, the Sharks announced in a statement.
Sharp reluctantly stepped into the role this season after head coach Shane Flanagan was suspended by the NRL for 12 months over the club's 2011 supplements program.
Noyce said it was sad to see Sharp go and thanked him for his contribution amid "extremely challenging circumstances".
"It was fitting that Peter departs on his own terms, that being on the back of a record-breaking comeback win for the club last Friday night in Brisbane," the CEO said.
"The club certainly appreciates his efforts in what has been a very difficult season and - while he may have expressed a reluctance to take on the role when first handed the reins - once appointed, Peter worked exceptionally hard and always acted in the best interests of the players and the club."
Sharp, who made it clear from the outset he had no ambition to take on the first-grade coaching role, said he believed the decision to quit was the correct one for both him and the club.
"I thank the Sharks for the opportunity both as an assistant and as the head coach, even with the challenges we've faced this year," Sharp added.
"But I think the decision I've made to step down is in the best interests of the club and I believe for me it is in my best interests as well.
"I hope the players can fulfil their potential and finish the season on a positive note."
Late last month, Sharks skipper Paul Gallen launched an extraordinary attack on his embattled club, saying players were not giving their all because they were under the impression Sharp wasn't.
"I think that's been the problem throughout the year," he told Triple M radio on June 22.
"I don't think players have been putting 100 per cent in because they're under the impression Sharpy isn't putting 100 per cent in.
"I just think we've lacked direction there throughout the year."
The Sharks said they would appoint a coaching replacement in "coming days", with the likes of Tim Sheens, David Furner and Brett Kimmorley touted as potential candidates by pundits.
The news came less than 48 hours after playmaker Todd Carney was sacked by the club after a lewd photo of him was posted on social media.
Cronulla are anchored at the bottom of the NRL ladder, with just three wins in 14 games - including last round's upset 24-22 victory over Brisbane.