(CNN) -- As a swimmer, his countless hours of training paid off handsomely -- earning him a record 18 Olympic gold medals.
As a golfer, Michael Phelps is wondering what he's got himself into.
"It's one of the most humbling games I've tried to do in my entire life," the American tells CNN.
"I could always pick things up fairly easily, but I don't get how hitting a little object -- a little white ball, that isn't moving -- is so hard.
"Why can't I just hit this in a straight line? Or hook it, or draw it, or fade it -- I can't do it. I'm finally learning how to be able to do all that stuff and do it consistently. But I still do have some pretty bad shots."
Have a quick look online and you'll find Phelps hurling his driver away in disgust after embarrassingly topping his tee shot at the home of golf, St. Andrews in Scotland.
"Throwing clubs, using profanity -- everything comes out," Phelps says.
But there are some moments of magic, such as when -- as a 26 handicapper -- he sank a monster 150-foot putt at the Dunhill Links pro-am in Scotland last October.
However, golf requires both power and precision -- which Phelps, who was diagnosed with attention deficit disorder as a child, is slowly learning to combine.
"He's one of those players that people would look at and say, 'He has a lot of potential.' What that technically means is that the player is very long and very wild," says Tiger Woods' former coach Hank Haney, who has been tutoring Phelps in the latest series of his television show The Haney Project.
"They never look at someone who hits it a very short distance and say, 'Oh you've got a lot of potential.' They always comment on the potential someone has as based solely on the distance of their hitting."
Haney has some history in shaping unpredictable talents, having previously worked with former basketballer Charles Barkley and boxer Sugar Ray Leonard among his celebrity TV clients.
"Michael is 6'4 but he has a 6'8 wingspan, so his arms are very long. Because of that he has a pretty long, loose swing," Haney tells CNN.
"It's capable of generating a lot of power ... That's been the biggest challenge, to get his swing better so he can control it a bit."
Haney says Phelps is "definitely getting better" after carding true hackers' scores of between 97 and 117 in six rounds immediately after the London 2012 Olympics -- where he took his career tally to a record 22 medals.
"His No. 1 goal after the Olympics was to learn how to play golf and be decent at it," Haney says.
"I think he's passionate about it. It's nice to have someone like Michael Phelps interested in the game, it's great for golf."
Golf is not only giving the 27-year-old Phelps a new hobby (if not quite a new career) -- it is also extending his commercial sell-by date.
While he's not in the $250 million league that Nike reportedly paid to sign up golf's new star Rory McIlroy, the "Baltimore Bullet" has already landed a club deal with Ping.
"Ping is a well-established global brand that should be able to deliver Phelps with huge international exposure," says British sports business expert Simon Chadwick.
"Phelps, meanwhile, provides Ping with a brand association that has a strong track-record of success at the very highest level.
"That said, this is a somewhat strange alliance that would be appear to be fraught with difficulty. It doesn't make instant sense, and quite what the tangible returns will be to both parties isn't necessarily obvious.
"If there is no expectation that Phelps will become a professional golfer, the Ping deal tends rather to imply that this is short-term opportunism -- unless, of course, the relaunch and rebranding of Phelps as a global sport or leisure brand starts here.
"If the Phelps brand in golf is to have any sustainable future, he needs to start delivering the kind of performances that fans and consumers will be looking for."
Haney doubts that Phelps will be able to make it as a pro golfer, citing the very few examples of sports stars who've been able to switch to the game -- and most of those have been on the seniors circuit.
"The possibility is there, but golf seems to take more time than any other sport -- there's so much to learn and so much to practice. You have to dedicate full-time to golf to get there," Haney says.
"It's a big difference between being a scratch golfer or two handicap and being a professional golfer. It's a whole other world," Haney adds when asked about the golfing prospects of retired tennis star Andy Roddick, who like Phelps has been hitting the celebrity pro-am circuit.
And Phelps sounds like he's enjoying his retirement too much to dedicate himself to the same punishing routine that saw him not miss a 6.30 a.m training session for six years -- as Haney was informed by his protege's former swim coach.
"I've been saying a lot more recently about how great it is to be retired," says Phelps. "I can wake up at 10 in the morning, grab a cup of coffee, read the newspaper.
"If I feel like hitting a couple of golf balls, I hit some golf balls. I really just hang out, and it's awesome.
"At this point I'm really just trying to enjoy the sport, learn the sport, and be able to beat all of my friends who I go out and play with."
However, Haney is in no doubt that Phelps is committed to his new adventure.
"The crossover is the work ethic that he has -- he knows what it takes to be great in sports," the 57-year-old coach says.
"He's used to being coached, that makes it easier for me. In golf you have to be coached, no-one just knows how to do it. In order for that to happen, you like to have someone that's used to taking coaching."
For someone who has coached 14-time major winner Woods, the goals of a novice like Phelps ("He's thinking pro-ams and playing amateur golf. He'd love to win a club championship one day") bring Haney back full circle in his career.
"Tiger was my last student and I had determined that when I started with Tiger, I said he's going to be the last touring pro that I have," says Haney, who wrote a book detailing his six years working with the biggest name in modern golf.
"I taught touring pros for 32 years and I enjoyed it. It was incredible, a lot of great experiences, but 32 years was enough for me -- I taught over 200 touring pros. It was time for me to do something different. And where do you go from Tiger Woods?"
Apart from his TV show, Haney is now focused on his corporate work, his International Junior Golf Academy based at Hilton Head, South Carolina -- and taking the game to the people.
"Golf's been awful good to me, I have no problems doing that, I'm very thankful to the game of golf," says Haney, who is an active presence on Twitter, giving away tips to anyone who contacts him -- much to the chagrin of some of his peers.
"Last year I did clinics for over 15,000 people, so I feel like through Twitter and doing the clinics I'm much more able to reach a larger audience and giving back to the game a little bit.
"I enjoy being a top instructor who is willing and able to do those things."
He says his junior academy, which has almost 150 students from 22 countries, is not necessarily seeking to unearth the next Tiger Woods.
"I'm really proud of the fact that the kids don't just learn golf but they have a great education. Every kid from our academy last year went to college, 94% of them got scholarships. I really enjoy seeing how much they grow as people from being in our academy."