But Fleetwood's second on the par-5 finishing hole leaked right and splashed into the water, and once his attempt at a miracle hole-out after a drop from 120 yards didn't fall Im could finally exhale as the winner.
That's when Im could hug his caddie in the locker room, where he watched the last 20 minutes or so on a monitor.
"I've been in this spot many times. ... I just felt like the experience really helped," Im said through a translator.
Some of Im's best moments have come when no one has been looking.
He was third at the Zozo Championship in Japan last October, a finish totally overshadowed by Tiger Woods tying the PGA TOUR record of 82 career victories. And in November he went 3-1-1 to tie for the best showing by a player on the International Team at the Presidents Cup, but the U.S. Team captained by Woods rallied in Singles on the final day to win the trophy at Royal Melbourne.
But this time, he was on center stage and embraced the moment.
Hughes and Im went to the par-3 17th green -- the end of the "Bear Trap" three-hole stretch -- in wildly different spots. Im stuck his tee ball to just inside of 8 feet, while Hughes had nearly 55 feet left from above the hole.
Hughes rolled in his most improbable birdie to an enormous roar, pulling into a tie with Im at 5 under.
If Im was worried, it didn't show.
Im took a couple looks at his downhill line, took his putter back just a couple of inches and watched the ball roll in for a birdie that allowed him to reclaim his lead at 6 under -- this time, for good.