In the seats high above the Sydney Aquatic Centre dive pool, Matthew Mitcham is wearing a printed white T-shirt and blue jeans, his blond hair neatly cut, and is pondering life beyond elite sport, with the caveat his ambitions are subject to revision week by week. “I’d like to discover new things, help to change the world,” he reflects.

Chlorine blankets the air and a coach’s booming voice echoes from the adjacent swimming lanes, the water jets gushing and splashing. Mitcham’s talking about a career in medicine, maybe, whenever he stops diving: “I think everyone deep down wants to do that; leave their mark on the world.”

Ah, but a year ago at the glowing blue Water Cube at the Olympic Games in Beijing, Brisbane-born, Sydney-based Mitcham left an indelible mark. He achieved the highest-ever diving score in Olympic history with his back two-and-a-half somersault with two-and-a-half twists in the pike position.

Then, in the spectator stands before the world’s media, he briefly kissed his Sydney-born partner, marketing strategist Lachlan Fletcher, and gave him his bouquet. No sweat. “The apple doesn’t fall far from the tree,” declared his short, beaming mother, Vivienne, who was also by his side as her boy earned a perfect score of 10, “I don’t know who cried more; him or me.”

Six months later, he danced with gay abandon on the lead float as chief of parade along Oxford Street, and surely, the throng who had turned out for the 2009 Sydney Gay and Lesbian Mardi Gras must have pondered, there were few secrets in the life of Matt Mitcham, now age 21-and-a-half.

But, it turns out, he has much unfinished business to mull over, both career-wise and personally.

First up, though, how do you improve on perfection, much less repeat it? In July Mitcham failed to replicate his Olympic heroics at the FINA Swimming World Championships in Rome, dropping from second to finish fourth after his final crack at the ten-metre dive, his pet event.

He may be “too nice for his own good”, thundered a sports correspondent in Rupert Murdoch’s Australian tabloids when Mitcham declared his belief in “karma” was behind his decision not to name 15-year-old diver Tom Daley as his main threat in Rome and therefore avoid pressuring the fresh British competitor.

Daley ultimately took gold and Mitcham therefore “doesn’t have the killer instinct that others use to exploit their rivals’ weaknesses”, the writer moaned, as though the sport were all about press conference bluster as opposed to performance.

Mitcham fortunately hasn’t allowed the five-cent sports page psychoanalysis to warp his natural nice guy instincts, nor curb his openness about his life and his sexuality, revealed in The Sydney Morning Herald in May last year.

The matter-of-fact outing lead many to speculate he’d be denied lucrative sponsorship deals until Telstra finally stepped up to the plate – but it’s his only major sponsor thus far. “[We] don’t know whether that’s because of the global financial crisis or because of my sexuality,” confides Mitcham.

He’s back training at the pool after a short holiday in London, to which he’ll return for the 2012 Olympics to defend his gold, but first up there’s the Commonwealth Games next year in Delhi.

The mid-20s is considered the peak time for a diver and Mitcham will be 24 when the next Olympics are held. “I’ve changed a lot of things since Beijing,” he reveals. “That may sound ludicrous given I won the Olympic gold, but the rest of the world is advancing quite quickly in difficulty and quality.

“I have to improve at an even faster rate, so this year and the next will be very experimental with technical changes and using a few different dives as well. I’m trying to increase my degree of difficulty. Hopefully I’ll have that consolidated by the time London comes around.”

Wisely, he’s keeping his signature back two-and-a-half somersault dive with two-and-a-half twists in the pike position, “but I’m upgrading the other ones”.

He “never” toyed with retiring after Beijing, despite one report to the contrary: London has always been and remains the goal, and there he hopes to get several medals.

Diving, he maintains, “is all subjective. You can think it’s absolutely brilliant and your coach can think it’s absolutely brilliant too, but it’s all up to the judges. So you can’t really know if you’ve done a great dive”.

Mitcham is training six hours a day across eleven sessions a week – including gym strength and resistance work – on top of his bachelor of arts-science studies at Sydney University, with majors in science and languages, including French and Spanish. Vivienne, who has also moved to Sydney, works at a bar at the university; his mother has worked a number of jobs over the years.

Mitcham is unsure whether he’ll take any more lessons in Mandarin, which he was learning a couple of years ago in Queensland, even though it might come in handy conversing with his competitors. “There were just me and two Chinese boys in the doping control room after the Olympics,” he recalls with a smile. “They didn’t look happy, so I didn’t feel like I should have been practising any of my Mandarin.”

Growing up in Camp Hill and Carina, seven and eight kilometres south-east of Brisbane respectively, Matthew Mitcham had been born on March 2, 1988, but knows little about his father. What sort of background does his dad have? “I don’t know; I’ve never met him,” Mitcham says quickly and dismissively.

What’s the story? “They [his mother and father] just separated before I was born. But there’s not really a big story. There was no animosity or acrimony there. I’ve just never met him. I have not been interested enough to pursue meeting him.” Mitcham knows his father’s name, but “I don’t want to [reveal it],” he says. “I don’t think that’s fair on him.”

Vivienne raised her son not with any particularly religious framework but with some solid “life rules”: “I have very strong morals and values, the same as her,” he says. “That’s kept me in vaguely the right direction.” Such as? “The very basic ethics: you don’t hurt other people. Moral fibre. And she let me do the rest of my own learning. I think I turned out all right.”

Mitcham – who has a much younger half-brother, Marcus, age 12, who is still at home in Brisbane and with whom he’s mostly been communicating by text message the past couple of years – had a rebellious streak, getting his tongue pierced at 14. “I was a normal kid; I just did things differently,” he says with a shrug.

His normality was not evident on the sports field. “I tried everything I could; I just wasn’t good at anything,” he says. “I tried a whole heap of stuff and I played all the games at lunchtime with all the other kids: soccer, football, all that other stuff; I was just terrible. I was just lucky that I found my niche.”

At first, Mitcham thought that niche was trampolining, until he took up diving at 11. “Brisbane summers are really hot, and one of the houses I grew up in was close to the Sleeman Aquatic Centre,” he recalls. “I’d use the diving boards there – other people would do bomb dives but I’d do a double back flip into a bomb dive.”

One Saturday, a senior Australian Institute of Sport coach, Wang Tong Xian, saw Mitcham backflip and bomb dive and offered him a place being coached.

But five years later, Mitcham’s 16-year-old body was wracked by a lower back stress fracture and joint and tendon swellings in his wrists. He quit diving, feeling wrecked mentally, physically and emotionally, expecting not to return to the sport.

“I did burn out, because I was doing too much,” he admits. “I’d been suffering from depression for a couple of years. I was medicated for a couple of years. I didn’t know anything outside of routine … I’d come to hate diving, and I really didn’t want to come back to it.”

During the break and taking a holiday in Sydney in 2006 to let his hair down, Mitcham met his partner, the taller, brown-haired Lachlan Fletcher, who “made me see what a normal life was like without diving, because I didn’t know what to do with myself. The real world’s not that scary.”

Fletcher had just moved to Brisbane to be with Mitcham when Mitcham’s current coach, Chava Sobrino, rang and talked the diver into returning to Sydney to take up training here. So Mitcham and Fletcher packed their bags and returned south permanently.

Does Mitcham see his coming out as brave, more than a year on? “I don’t see sexuality as influencing my beliefs or opinions or perceptions of anybody, whether they’re gay, straight, bi, trans, experimental, I don’t care. I see it as a very uninfluential factor in people.”

After Beijing, many gay kids wrote praising Mitcham, “and that was really nice, really humbling”. Mitcham had always been aware of his sexuality, he says. “Mum told me she knew before I did,” he says with a grin. “I don’t know how she knew; she’s very perceptive. She’s like a fag hag, so she kind of knew.”

Growing up, he had ambitions to be a doctor, though he has said he lacked the attention span required, yet he hasn’t shut the door on such a career: “It depends on how well my studies go. I think I’m capable of doing whatever I want to, as long as I put the work into it.

“I’ve got a flexible degree so I can dabble in so many areas. Then I can do whatever postgraduate degree I want.” Mitcham is interested in medical research, genetics and pharmaceuticals. “I’m not really interested in being a GP, but that’s just an opinion I’ve had for the last couple of weeks. I change my mind all the time. I could end up wanting to be an emergency room doctor.”

Mitcham says his partner Fletcher has lived the demands of diving now for more than three years. “Obviously he’d like more time with me, but he knows this is what I do, that’s it’s not just my job, it’s my passion, so he understands …

“He’s a pretty shy person. He works quietly to put me into the spotlight and I work on trying to not put him unnecessarily there.”

Would they marry if such legal reform could be achieved for same-sex couples? “I know a lot of people who want to have their relationship recognised legally, and I would really like them to have their wishes,” says Mitcham.

“I haven’t thought about it [for he and Fletcher]. There are too many other things immediately pertinent to me, like my sport and my study. I’m 21, and I don’t think 21-year-olds should be married.”