He recalls the moment the ball dropped along with his jaw.
"The ball landed on the fringe and I thought to myself 'that was a good shot', then the ball just disappeared."
"I couldn't really believe it, I thought Dad was joking."
The Napier Boys' High School student credits his accomplishment to a last-minute lesson from golf professional Glenn Robinson.
"He told me to work on my thumb grip and my foot placement. I could feel that my swing was a lot better."
He went on to shoot his best ever round of 89.
Father Mark Keating, who has played the game for 30 years without a hole in one said it was an "awesome moment" to share with his son.
"It was very exciting," Mr Keating said.
He sees a big future in the sport for his boy.
"I have no doubt he will break 80 before the summer is over."
Josh's ultimate ambition is to one day be on the PGA tour.
He currently played off a 20 handicap which his father said would be whittled down "in no time".
His idols are Jason Day and current world number one Jordan Spieth.
The most satisfying aspect of the sport for Josh is hitting a clean drive off the tee and seeing the ball sail straight down the fairway.
Mr Robinson said the timing of the hole in one was perfect.
The Hastings Golf Club is having an open day this Sunday, October 11.
There will be a hole-in-one competition on the same hole Josh got his hole in one.
Anyone able to sink a hole in one will walk away with a new car, a Suzuki worth $20,000.
The open day will run from 10am to 2pm and the hole-in-one competition is open to all members of the public.
