What makes Eric Murray and Hamish Bond tick? It's doubtless a question their rivals have pondered at length as they search for clues on how to break their seven-year monopoly on the coxless pair discipline.
Their achievements - never beaten in the pair, 61 successive victories across seven world championship finals, including a coxed pair crown with Caleb Shepherd in 2014, 21 event titles without a single defeat - make them unbackable favourites for a second Olympic crown in Rio in August.
But who are these men: peas from a pod, similarly driven to an extreme, or opposites who make an unbeatable whole?
The truth lies in between.
They might share a Twitter account and part-own a racehorse together but they have their own lives away from the water and are distinctly different personalities.
Murray, 34, Hastings-born but of the Waikato, is more extroverted, with an occasional amiable larrikin streak. Bond, 30, of Otago, is the more studious.
Both are married and Murray has one child so they're certainly not joined at the hip but, in Bond's laconic words, laced with a grin: "We get on OK."
As Carl Meyer, a coxless four team-mate of the pair in 2007, puts it: "If you spend three months a year on tour, spend every day training together, you don't want to hang out on a Saturday night."
That year's four was when Bond first joined Murray, already a 2004 Olympian, on a boat. Those two, Meyer and James Dallinger won the world title.
Olympic glory beckoned in Beijing the next year, but things went wrong and they missed the A final.
Afterwards, Bond and Murray teamed up in the pair and have enjoyed unparalleled success. The longer they remain unbeaten, so the desire to keep it that way deepens.
They headed for Europe this week but the buzz of heading off to another high-octane international campaign was not what it once was to these seasoned veterans.
"It's definitely not the same as it used to be," Bond says. "All we can do is meet expectations. Because ours is to win, you can't do better than that. Now it's more about ticking it off as we go along."
Bond cheerfully admitted he didn't immediately warm to Murray when he joined the four.
Bond has a serious streak, is a driven man. Murray is more relaxed but has always turned it up when needed.
"We didn't really get on that well to start with. I didn't take to Eric's personality," Bond reflects.
"I was the new guy and it took him a bit of time to respect me, I think. It just took a few arse-whippings before he realised I could handle my way in the sport.
"Now I think we know each other pretty well, know each other's quirks, and try not to push each other's buttons too often.
"I'm probably more guilty of it than Eric. He's fairly laid-back, extroverted, but nothing fazes him too much. I perhaps can be a little bit more uptight.
"We get on OK. We have to and, fortunately, the biggest reason is we've never lost, never had to ask ourselves the really hard questions. It's pretty good conflict resolution. If you're always winning, you can't have too many conflicts."
Meyer, who is married to double Olympic champion Caroline (nee Evers-Swindell), reckons that the rarefied elite atmosphere makes it difficult to be really tight mates in any case.
"You're all in there under pressure and that amplifies things," Meyer says. "They are slightly different personalities, just like some people turn up early, some late; some want to party, some don't.
"In hindsight, the biggest thing is sometimes just accepting some of those differences rather than fighting them.
"Bondy's learned to maybe accept some of the differences, and maybe Eric's learned to accept some of Bondy's differences."
Meyer, affectionately nicknamed Boot Camp for his devotion to the gruelling regime required in the sport, admits he also found Murray challenging early on.
"I probably got rubbed up by Eric being a bit more laid-back, where I'm a bit more like Bondy - 'Come on, everyone's got to put in right now, 100 per cent every session'. But you've got to let people be who they are, give them a bit of room.
"Eric wasn't the guy who slaved away every day, but when the big time came, he'd pull it out. And he hasn't been caught short."
Meyer is not surprised the pair developed into world-beaters but admits surprise at their longevity.
"I never questioned their ability but in sport it's one thing to get on top, another to stay there. Hats off to them keeping it together as they have," he says.
Murray puts their time together down to a gradual shifting from being "a competitor to being competitive. Now we're expected to go out and do it."
He says the pair would be "stupid" if they didn't realise they will arrive in Rio with a target on their backs.
"If you're in a position of being another crew coming in trying to take down a crew like us, that's a massive carrot.
"So we've got to make sure we're not allowing people to do that. The moment you take the opposition for granted is the day you get beaten."
Success has clearly forged a tight link, regardless of their different personalities. It has come down, as Bond put it, to "not wanting to let each other down".
"We're two of the strongest athletes in the world at what we do and we combine well."
Simple as that.