He is one of those Australian sportspeople that some Kiwis love to hate, but he's actually, according to those who know him well, "a bloody nice guy", "cool" and "down to earth".
Spithill is famously competitive. That came through during the2013 America's Cup, with a series of barbs and jibes that cut deep at Team New Zealand.
But he was just doing his job, finding a way to win for his team.
"He knew it would get under [Grant] Dalton's skin and rattle him," says compatriot and long-time former Team New Zealand sailor Adam Beashel. "He was like, well, if that is what is going to happen, this is easy to do. Say a couple of things and poke a little bit of stick.
"But when you get to know him you realise that's part of the game; that's the fun side of the game to him.
"You don't bag it. Instead, it's like, well, someone is going to say it so you may as well be the first person."
Spithill's presence in the 36th America's Cup adds a layer of spice and intrigue.
Dean Barker and Sir Ben Ainslie also bring profile, but for many Kiwi sports fans, nothing will quicken the pulses more than the prospect of taking on Spithill again.
Spithill's journey into New Zealand's consciousness started in San Francisco. The daily press conferences were beamed into our living rooms, creating a familiarity with the bullish redhead. Who was this outspoken Aussie?
A flashpoint came with Oracle seemingly dead and buried at 7-1 down.
"I think the question is, imagine if these guys lost from here," said Spithill, as he glanced at Barker. "What an upset that would be. They have almost got it in the bag. So that's my motivation. That would be one hell of a story."
Former Oracle director of external affairs Tom Ehman was watching on beside the stage.
"You give Jimmy a little bit of a competitive edge, he catches fire," says Ehman. "You could see the colour drain out of Dean's face, as he recognised what [Jimmy] was saying. [It's] such a mind game, as are all sports at this level."
Spithill reflected on that moment in his 2018 biography 50 knots: Chasing the America's Cup.
"I sensed this was a situation I could use to put unexpected pressure on the Kiwi team: they had everything to lose," wrote Spithill. "I don't think such a thought had ever previously entered their minds, but now it had. This was a fight to the end."
The American team had been written off, but Spithill kept believing. He wasn't above questioning the belief of Team New Zealand, especially during the seven days when they were stuck on match point.
"Knowing him, when I was listening to some of the stuff leading into that regatta I thought 'far out, the American PR person has really got him saying the things he needs to say'," says Beashel, a veteran of four America's Cups, including three with Team New Zealand in 2003, 2007 and 2013.
"But he wanted to put that show on for his own team, more than for the media. He knew he needed his team to hear him saying what he needed to say."
Spithill became a bete noire for New Zealand, but earned respect from Herald journalist Paul Lewis in San Francisco.
"He was ebullient throughout the whole thing," says Lewis.
"He came across as an arrogant Aussie sometimes and we all groaned when we realised that Oracle were going to win because we thought he would be insufferable. But he was a good sport.
"Jimmy's a media pro. He drags his personality up a couple of levels to play it for the cameras and the sponsors."
The niggling and needling continued in 2017 in Bermuda. Remember when he stated that Team New Zealand had made "fundamental mistakes" in two round robin defeats to Oracle, or later claimed to know their preferred semifinal opponent, citing a "leak"?
He also "suggested" the Kiwi team needed a specialist tactician and did nothing to douse speculation of potential radical strategies, after photos circulated of Oracle team members taking a bow section from the Japanese team base.
Former Team New Zealand sailor Joey Allen, whose history with the syndicate dates back to 1995, was Oracle's crew coach ahead of the 2010 America's Cup match.
"I got to know Jimmy very well, I sat at a desk right beside him," says Allen. "I saw how he operates. He portrays himself very differently through the media. He's a really nice guy. Sure, he's a fighter, but he is also a cool guy."
New Zealander Harold Bennett was principal race officer for five America's Cups between 2000 and 2013 and observed Spithill at close quarters.
"If you didn't know better you could say Jimmy was an outspoken brat, but he is not really ... he is a bloody good guy," says Bennett.
Lewis agrees that the perception of the 41-year-old Sydneysider isn't always accurate.
"He's not as objectionable as a lot of people like to make out and that has been proved in this round, sailing for Luna Rossa," says Lewis. "He's a different kind of character because his bosses are different people, who do it a different way [to Oracle]."
To understand Spithill, first you need to comprehend his background.
He grew up in Pittwater, a small town 40 kilometres north of Sydney, that is surrounded by water, with a network of bays and estuaries and many houses only accessible by boat.
The Beashel family household, with Adam and fellow America's Cup sailor Colin, was nearby.
"Their house was across the bay," recalls Beashel. "It was a tight little environment and all about being on the water. There was a national park behind us and we were cut off from registered roads.
"You would come home from school, dump your bag and go out and play in the water or on your bike, until Mum would ring the bell for dinner."
Pittwater was a notoriously tricky body of water for young sailors.
"It made us, learning to sail there," explains Beashel. "A lot of people call it 'shift water'. It keeps you on your toes and learning. You knew it wasn't over till it was over.
"Every little race, you never knew what was going to happen. Those conditions made us and moulded us as fighters."
As a kid Spithill did odd jobs in the Beashel family boatyard – where older brother Colin was a local hero, having been part of the 1983 Australia II crew – and gained other local employment.
"He had some time running the tender service, which I used to do as well," says Beashel. "Running people back and forward to their boats in the 'tinnies'. It was a great way to grow up."
After competing in the Kenwood Cup and Sydney to Hobart race in the late 1990s Spithill was selected to skipper Young Australia at the 2000 America's Cup in Auckland.
The 19-year-old had the youngest crew, on the oldest boat. It was a gruelling apprenticeship – with four wins from 30 races – but a vital education.
Three years later he was with Microsoft-backed One World, put on the helm when Cup veteran Peter Gilmour (then 42) stepped aside for his promising compatriot.
Spithill eliminated Dennis Conner on Stars and Stripes, then Prada in the last four, before being stopped by Oracle.
He was snapped up by Luna Rossa for the 2007 Cup, advancing past nine other syndicates, before eventually being beaten 5-0 in the Louis Vuitton Cup final by Dean Barker and Team New Zealand.
His decade-long association with Oracle begun after that, with successful campaigns in 2010 (at 30, he was the youngest skipper to win the Cup) and 2013 followed by defeat in Bermuda in 2017.
"He has come a long way," says Beashel. "He started with a young match racing team that did the circuits. Some of that came into Young Australia and One World and then it gradually broke up. Being on so many different teams has taught him how to be a strong leader of people."
Aside from his obvious skills – he wowed the sailing world in 2007 with his dismantling of Chris Dickson's Oracle in the pre-starts, earning the nickname "Pitbull" – Beashel feels his greatest strength is a relentless "positivity and work ethic".
"He knows as a leader you have to show that," says Beashel. "If you are not showing it, how do you expect your team to come with you?
"That's why he gets so much credit for 2013. I'm sure if you could get the honest answer there was probably less than a handful [on the Oracle crew] that believed they could come back and win it. The rest had given up.
"But he was there every night and every morning saying 'we can do it'. I'm sure a lot were thinking 'yeah, we know you have to say that and believe in your own bullshit'.
"[But] he sniffed it and knew it was possible and you have to have that; if you don't have that there is no way you can make it happen."
Beashel took time to get over San Francisco, after chasing the Auld Mug since 2003.
But he was neighbours again with Spithill, as both had brought properties in Lake Macquarie, in Northern New South Wales, which bore a resemblance to their childhood surroundings.
"Jimmy recommended it to me," says Beashel. "I was looking for something like where we grew up."
As the families mixed and mingled, and the two sailors "mucked around" on their foiling windsurfers, one subject was off limits.
"It was one of those polite things," says Beashel. "Let's not talk about it [San Francisco] and just enjoy the fantastic environment."
But that time allowed Beashel to see another side of his compatriot, who hasn't allowed fame or fortune to go to his head.
"They had bought a little old beach house and it was just after the heyday of Oracle and the money, well there was no shortage of it," explained Beashel.
"But it didn't get bulldozed or turned into a mansion. It just got a bit of a renovation; when you walk in there is still the old velvet couches sitting there and carpet on the floor. They come up, treat it like a weekender and have a ball, with kids and stuff everywhere.
"He could have easily built a huge house, as most people do with investments around the area, but they didn't. It's still down to earth, you invite the neighbours around and it's not exclusive.
"That's how we were brought up and it was rewarding to see that he was still like that. He doesn't need all the luxury."
However, Spithill is still the ultimate competitor.
"I'm not going to lie, I want revenge," he told Sailing World in 2020. "I don't ever let any loss go. Defeat is nothing but education. We were too conservative [in Bermuda]. I love competition and [Team New Zealand] are the best out there right now. For me, this is another opportunity to go against the best."
Spithill, like Greg Chappell during the post-underarm cricket tours in the early 1980s or Quade Cooper at the 2011 Rugby World Cup, could encounter some hostility in Auckland but has deflected any of those questions.
"I think Kiwis respect someone who doesn't give up, who fights for everything, but ashore is honest and candid when asked a question," he said last year.
"I've always had a lot of fun in New Zealand. I've had some awesome battles over the years with the Kiwis, and I'm looking forward to a few more."
Heading into the Cup racing?
• Be aware that traffic will be busy, and parking will be very limited.
• Give yourself plenty of time and think about catching a ferry, train or bus instead.
• Make sure your AT HOP card is in your pocket. It's the best way to ride to the Cup.