Green started the final round of the US PGA Tour event three shots adrift of Colombian Camilo Villegas and shared second place with Fijian star Vijay Singh at eight under par.

What unfolded was disastrous.

A veteran of four years on the biggest golfing stage in the world, Green still had control of his round at two-over-par through the first 14 holes.

But it unravelled on a three-hole stretch of the PGA National's Champion Course known as The Bear Trap.

Designed by golfing great Jack Nicklaus, the par-three 15th, par-four 16th and par-three 17th holes have a warning sign for golfers before they start the water-laden stretch: "You are now entering 'The Bear Trap'. It should be won or lost right here."

Green wasn't happy with the way he was hitting the ball prior to entering The Bear Trap, and his mood had only deteriorated by the time he left.

He found the water at the 15th hole and walked away with a double bogey, before making par at the 16th. At the 17th hole he failed to carry the water but his ball was still visible so he decided to play it.

"It was just too tempting for someone of my IQ," Green laughed. "When it went back in, I thought I might as well keep going."

Green hit the ball out only to watch it land a metre up the slope and roll back into the water.

His second shot was a repeat of the first. On his third attempt he got the ball out of the water and onto dry land. Amazingly, a second ball, buried and invisible in the mud, came out as well.

He chipped onto the green and sank a long putt for triple bogey and the crowd roared when he pumped his fist after the ball dropped.

"I was lucky to make six in the end, but to be honest I was hitting the ball really badly before that and I was just trying to get in at four-under," he said. "I was struggling with my putting all week, and for me to be in contention without putting well is a rarity.

"When I'm under pressure I tend to lose it right a lot, and that started to happen from about the 12th hole onwards.

"I was hitting it OK on the front nine and I could've put some pressure on him [Villegas] early if I had putted better."

Green signed for a seven-over-par 77 to finish in a tie for 12th place at one under par.

Green pocketed $US109,760 ($120,807) - almost $500,000 less than if he had finished outright second. The result took his earnings for the year to $US359,340 ($395,000) and he jumped from 69th to 47th on the money list.

Villegas was the runaway winner at 13-under-par and finished five strokes clear of American young gun Anthony Kim in second place.