The win lifted the Sharks to 32 points alongside Manly and Melbourne, but categorically ended the Rabbitohs’ slim finals hopes.
In the night’s other match, the North Queensland Cowboys subjected the Bulldogs to a 36-12 towelling at Lang Park in Brisbane but still stayed bottom of the ladder.
In Cronulla, a 10-1 penalty count kept the Rabbitohs in the game in the first half but some trademark Sharks defence saw Souths miss a number of scoring chances to give the hosts a 12-8 half-time lead.
But three tries to the Sharks after the break extended the margin to 28-8 and ensured they had enough points to weather a small Rabbitohs’ fightback.
The first of those tries came just three minutes into the second half when a set play from a penalty saw quick hands to Brett Kearney whose pinpoint long ball found Luke Covell’s chest and unlocked the overlap for him to cross in the corner.
The Rabbitohs’ defence was absent again in the 55th minute when Brett Seymour waltzed untouched through the defence.
And just five minutes later a careless pass from Souths half-back Chris Sandow was intercepted by David Simmons and again he was unopposed on the way to the line.
The Rabbitohs clawed some points back four minutes later when a deft one-handed pass from centre Beau Champion set Nathan Merritt up to sprint to the line.
After the game Sharks captain Paul Gallen conceded that coach Ricky Stuart had been fuming at the rash of first-half penalties.
“Silly penalties, silly back-chat, silly dropped balls 20 metres out from our line,” he said.
“Fortunately we learned from it in the second half. But against teams like the Warriors and coming into semi-final footy we’re going to have to fix that, and it’s part of our game we’ll work on.”
Asked if he was confident that the Sharks could mix it with fellow ladder leaders Manly and Melbolurne he said: “That game last night was a class above any other club match this year.
“It was a great game to watch, and we’re probably a little bit off that yet. But there’s still five weeks of semi-finals and that’s something we have to build to.”
In Brisbane, two tries to Ty Williams and others to Carl Webb, Ray Cashmere, Sione Faumuina, and Ashley Graham saw the Cowboys snap a massive 13-game losing streak.
Ben Barba and Andrew Emelio scored the only tries for the Bulldogs, who have now conceded 122 points and scored only 16 since the controversial departure of Sonny Bill Williams.
Sharks too strong
In Cronulla, a pair of tries to centre Ben Pomeroy had given Cronulla their 12-8 lead at half-time.
Pomeroy asserted himself in the eighth minute when he cut back on the inside, ran past Sandow, and shoulder-charged the post as he was brought down near the line.
Pomeroy’s momentum carried him around the post to touch down.
The centre scored again in the 25th minute after a Greg Bird flick pass came off a South Sydney hand and Pomeroy powered over the line with a pair of defenders in tow.
But some inspirational play from the young Sandow and veteran David Kidwell put the Rabbitohs back in the game in the 25th minute.
Sandow’s 40-20 kick gained valuable ground and a clever off-load from Kidwell popped the ball out for Beau Falloon to score his debut NRL try.
The Rabbitohs piled on the pressure in the final minutes of the half but the Sharks’ defence was outstanding to preserve their slim advantage.
Sharks: 28 (B Pomeroy 2 L Covell, B Seymour, D Simmons tries; L Covell 4 conversions)
Rabbitohs: 14 (B Falloon, N Merritt tries; C Sandow 1 penalty, 2 conversions)