England's Hull kept the lead by limiting the damage to a bogey on the 18th hole at the Pelican Golf Club after hitting into the water following a lengthy wait that led them to finish in near darkness. That gave her a two-under 68.
Korda was poised to tie for the lead when she hit the tricky 18th green about 30 feet away. Her birdie putt down the slope and with the grain toward the water still ran out 4 feet, and she missed the par putt and shot 67.
Both are among the quickest players on the LPGA. Neither was happy about how it ended.
"It's kind of hard when you don't really see. I think it was a little bit of poor planning by starting so late for us," Korda said.
Hull was at 12-under 198, one shot clear of Korda and Zhang Weiwei, who finished much earlier with a 62. Zhang is No.106 in the Race to CME Globe and needs to finish in the top 100 to keep a full LPGA card for next year.
The weekend looked to be a duel between Korda, the LPGA player of the year, and the carefree Hull. That's how it looks for the final round, though it certainly didn't start out that way.
Korda, who began Saturday two shots behind, had a pair of bogeys in her opening four holes and failed to birdie the par-5 seventh. Hull had two birdies to stretch her lead over Korda to six shots before the American staged a recovery.
The top 60 after this week advance to the CME Group Tour Championship, where the winner of the season finale gets a $US4 million prize.
Australian star Minjee Lee went into this event in some danger of missing the Tour Championship at No.56 in the points race.
But she looks set to advance and join countrywomen Hannah Green (No.6), Gabriela Ruffels (No.28) and Grace Kim (No.43) there after shooting a 69 to be tied 11th, six shots behind Hull.
Ruffels was tied 36th at two under after a 71, while fellow Aussie Hira Naveed was tied 68th after a 73 and is set to miss the Tour Championship after starting the week at No.72.
Steph Kyriacou went into the week on the brink at No.60 but also looks set to miss the finale after missing the cut on Friday.
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