St George Illawarra's chances of qualifying for the NRL finals have taken a huge hit after they gave up a 12-point lead to the Sharks on Thursday night.

The Dragons appeared on track to score a boilover victory against their local derby rivals at Sharks Stadium but they went from being 18-6 up to losing 30-18.

Cronulla ran in four unanswered tries in the second half to put a major dent in St George Illawarra's hopes of sneaking into the playoffs.

Heading into their third and final bye next week in Round 16, the Dragons are sitting in 12th spot on the ladder with a 5-8 record.

They will probably need to win at least eight of their remaining 11 matches to have any chance of figuring in the playoffs.

The Dragons host Parramatta in Wollongong on 28 June in their next martch before they face a tough run against the Raiders, Roosters, Bulldogs, Cowboys and another clash with Canberra.

On current form, they could be well out of the finals hunt after that stretch.

They started slowly against the Sharks but after conceding the first try, they equalised when veteran hooker Damien Cook crossed the stripe

Rising star Lyhkan King-Togia notched a clever individual try and when the Dragons made it three tries in a row before half-time with Sharks centre Jesse Ramien in the sin bin, they went to the break holding a commanding 18-6 advantage.

But they had a series of fumbles from high kicks and gave away silly penalties as the Sharks drew level and then went ahead following a try to winger Sione Katoa.

With the match in the balance and the Sharks clinging to a six-point lead with less than 10 minutes left, the Dragons were on the wrong end of a controversial call from referee Grant Atkins from a kick restart which left coach Shane Flanagan up in arms.

Dragons centre Moses Suli batted the ball back while over the 40m line after the kickoff from halfway but the referee ruled the ball had not travelled 10 metres so he gave the Sharks a penalty, which led to Katoa scoring again to ensure victory for the home side.

Flanagan was "amazed" at that decision and a few others which went against his team.

"There's a red line there that's called the 40-metre line and Moses Suli was on the other side of the 40-metre line," he said in the post-match media conference.

He conceded the Sharks "ran a little harder in the second half, got good field position and all their kicks were contestable".

"We didn't handle the kicks."