Defending champion Sergio Garcia matched the worst one-hole score in Masters history with an octuple-bogey 13 at the par-5 15th hole in Thursday’s opening round at Augusta National.

And the 38-year-old Spaniard says he doesn’t feel like he hit a bad shot on the 530-yard hole, even though he plunked five of them in a row to a watery grave in the pond guarding the green.

Splash. Splash. Splash. Splash. Splash.

“I don’t know what to tell you. It’s one of those things,” Garcia said. “It’s the first time in my career where I make a 13 without missing a shot. Simple as that.

“I felt like I hit a lot of good shots and unfortunately the ball just didn’t want to stop. So it’s just unfortunate, but that’s what it is.”

It became a real-life version of the movie “Tin Cup” with Garcia in the Kevin Costner role of Roy McAvoy, who refuses to quit until he makes a shot even as his chance at victory vanishes with balls rolling off the green into the water.

“I kept hitting good shots with the sand wedge,” Garcia said. “I don’t know why the ball just wouldn’t stop.”

Garcia was level for the worst score on any hole played in Masters history, the other 13-stroke efforts coming from Tommy Nakajima in 1978 at the par-5 13th and Tom Weiskopf in 1980 at the par-3 12th.

It’s the worst Masters score on any hole outside famed Amen Corner — the 11th, 12th and 13th holes that often decide Masters glory.

“With the firmness of the greens and everything, I felt like the ball was going to stop,” Garcia said. “Unfortunately, for whatever reason, it didn’t want to.”

Garcia hit that ball with a mind of its own off the tee to 206 yards from the pin, then used a 6-iron from the fairway on his first try.

“I thought it was perfect. Straight at the flag,” Garcia said. “If it carries probably two more feet, it’s probably good. And if it probably carries a foot less, it probably doesn’t go off the green and probably stays on the fringe.

“But unfortunately I flew it on the perfect spot for it to come back.”

Garcia then moved to the relief area to try again, and again, and again, and again before mercifully reaching the green and ending the misery.

Ninth-ranked Garcia, who birdied the par-3 16th after the horror show, finished with a nine-over par 81 in his first round as a major defending champion, a nightmare epilogue to what had been the Spaniard’s feel-good story.

Garcia won his first major title on his 74th try at last year’s Masters on what would have been the 60th birthday of his idol, the late Masters champion Seve Ballesteros.

Since then, Garcia got married, wearing his champion’s green jacket at the wedding reception, and last month became a father, naming his daughter Azalea after Augusta National’s 13th hole.

Don’t expect any siblings named Firethorn — the name of Augusta National’s 15th hole.

– ‘The rest is history’ –

There was no consolation for 17 other holes played at one-over par.

“Not really,” Garcia said. “I shot 81, which is not great. I was fighting hard. I was doing quite well.”

But Garcia lipped out a birdie putt at 13, his first competitive try at the hole named for his baby daughter. Then he made bogey at 14.

“And then, obviously,” he said. “The rest is history.”