Sharks halves Nicho Hynes and Braydon Trindall starred on a Sunday afternoon that Foran said went "horribly wrong" for 10th-placed Manly and ended in his biggest loss as coach.
"We saw it as an opportunity to get our season back on track and we just didn't fire a shot," Foran said.
"It just went wrong for us. It went horribly wrong, just both sides of the ball.
"We're clearly low on confidence and that's affecting our flow with the footy and then on the other side, it's affecting our decision-making defensively."
It's been quite the fall from grace for the Sea Eagles, who rose from the doldrums and won eight of 10 games immediately after Foran replaced Anthony Seibold.
Manly have since lost five of six, and for the first time under Foran, they were never in the contest at home.
The Sea Eagles (9-10) have a losing record for the first time since round six and must win at least four of their last five regular-season games to play finals.
They are four competition points out of the top eight and have tough clashes against Newcastle, the Dolphins and Warriors on the run home.
"I'll say one thing, we're not done with yet," Foran said of Manly's finals hopes.
"We know where we want to go, and where we want to head this season and we won't be backing down from that."
The Sea Eagles' playmakers gave away four seven-tackle sets with poor kicks.
Reuben Garrick sprayed the kick-off out on the full after the Sharks' fourth try and put the visitors in place for Sione Katoa to score their fifth only minutes before the half.
Tom Trbojevic's replacement Lehi Hopoate had an afternoon to forget at fullback, notably spilling a regulation Hynes kick directly ahead of the Sharks' third try.
The fourth-placed Sharks won an eighth game from nine starts, on the same weekend as unconvincing performances from premiership rivals Penrith, the Sydney Roosters and Warriors.
After fulltime, coach Craig Fitzgibbon scoffed at a question as to whether the Sharks were finally taking the step from good to great this year.
"To be honest, I think it's your (the media's) impression of us. We've been consistently up there for four years straight, just without any 'they're a threat' mentality," he said.
"I don't know why the perception has changed that we're believable now.
"We just don't believe if anyone believes in us, anyway. We haven't had it for four years, we're not going to start doing it now. We're just going to believe in each other ... there's still a long way to go."
So long a lightning rod for criticism, halfback Hynes is playing as well as he has since winning the Dally M Medal in 2022.
He embarrassed the Manly middle barging over for the Sharks' fourth try and sent a bullet-like pass for Ronaldo Mulitalo's second try just after the break.
Hynes dummied through rookie five-eighth Joey Walsh, who had a difficult day, and then passed inside for Sifa Talakai to score in the second half.
He also kicked a career-best 26th consecutive goal and finished the afternoon with three line breaks.
Trindall's suspect ball to Teig Wilton gave Cronulla their opening try, before the five-eighth floated a lovely cut-out pass for Mulitalo's first.
He kicked past Hopoate for KL Iro to cross with 15 minutes to play.
Just before halftime, the Sea Eagles lost second-rower Ben Trbojevic to his second game-ending head knock in as many appearances.
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