After weeks of questions around his role in the halves, Hynes scored twice and helped lay on Cronulla's two other tries on Friday night at Shark Park.
The win snapped a run of four losses in five games for Cronulla, and had them replace the Dolphins in the eight.
It didn't come easy, after the Sharks' 14-0 lead shrunk to 14-12 in the second half and big Toby Rudolf was left to make a miraculous try-saving play chasing back on a kick.
But with the game on the line it was Hynes who also proved the difference, slicing through the Dolphins' defence for his second try with five minutes to play.
He then added the icing to the cake, with a long cut-out ball sending Sione Katoa across on the siren.
Cronulla coach Craig Fitzgibbon had ruled out any prospect of moving Hynes from halfback to No.1 after the Sharks' loss to Melbourne a fortnight ago.
But on Friday night, Hynes did his talking on the field, particularly busy and running the ball regularly.
He scored the Sharks' first in that fashion, running between Herbie Farnworth and rookie Dolphins winger Tevita Naufahu to go over.
Cronulla weren't able to make use of more good attacking ball before the break, but it was Hynes who helped extend their lead after it.
After slotting a penalty goal from close to the sideline, the halfback engineered  Cronulla's next when he put Briton Nikora over the advantage line.
Nikora then offloaded for Jesse Ramien to score, making it 12-0 before another penalty goal took the lead to 14 before Hynes late-match sealers.
Hynes, Brailey and Nikora were the stand-out players in attack, but the Sharks defence was equally impressive for the first 65 minutes.
The Dolphins have been the attacking juggernaught of the NRL in recent months, averaging 45.6 points over their past five games and reaching 50 thrice.
At the same time the Sharks have been guilty of leaking points, letting in 164 points in the past fives games alone.
But on Friday night, the script was flipped.
With Kodi Nikorima missing for the Dolphins with a hamstring injury and Hamiso Tabuai-Fidow rested, Cronulla menaced their young halfback Isaiya Katoa.
Teig Wilton attacked the Tongan No.7, with Katoa turning the ball over on the last twice.
Katoa's only real success came with 13 minutes to go, when he put Sean O'Sullivan through a hole and the five-eighth kicked for Max Feagai to score.
Cronulla's defence was breached again four minutes later when Farnworth broke into space from within his own half to make it 14-12.
The Dolphins had the chance to steal the lead moments later, only for Rudolf's effort sprinting back to stop Jeremy Marshall-King diving on a grubberkick.
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