That eagle was part of a 5-under 67 that has him one stroke off the first-round lead.
"It was a 6‑iron, like 175ish (yards) playing about 10 yards further with the wind so I needed to take a little off of it," Spieth said. "Absolutely flushed it right at the hole and didn't think it went in. I started walking because balls have been sticking on the green so I thought it just stuck, but I guess it just crept forward that extra two feet. With very few people watching, you don't know if it's really close or in when they cheer and then you look up and the ball disappeared."
Thursday in the Bahamas sported temperatures in the mid-80s with high humidity. Players were drenched in sweat walking off the course, a layout with which they are still trying to familiarize themselves.
Spieth won this event last year by 10 strokes, with a tournament-record 26-under total. But that was at Isleworth Golf & Country Club in Windermere, Fla. Nonetheless, he expects another shootout this week.
"I'm very surprised that no one's lower than 6 under," he said, "but just gets a little tricky with the small greens, I guess."
As for that ace, Spieth has some friends on hand and he said he would celebrate - and share the wealth - with a few beers.
"When you come to the Bahamas, that's probably going to get pretty expensive out here," Spieth said. "But cool start to the day."