"A mate of mine was setting up some gyms in Dubai, so I helped run them for a while, then drifted back into rugby through fitness and conditioning, working with the clubs here.
"After that, the IRB put me into Iran for 18 months. This job as rugby manager for the UAE came up late last year, so here I am back in Dubai."
Iran and Dubai aren't the first places that come to mind in terms of coaching gigs and, without the luxury of a big staff, he has to spread himself around.
But Marsters is excited about the future: "Asia has the potential to be a rugby powerhouse. It's starting to get a foothold now - in Iran, where there are a lot of big, solidly built guys and there's a national tradition of combat sports, there's a real attraction for that kind of gladiatorial element.
"It's a pretty rugged set-up in places. I ran training sessions on the side of a mountain with goats on the paddock and you'd go down to the creek for a water break while the militia were wandering around with AK47s.
"But the people - their enthusiasm was just fantastic. And you get first fives with cauliflower ears - before training, whereas we might play touch, they're doing one-on-one wrestling. "
Locals in Dubai and Abu Dhabi are more slightly built, though there are doughy-looking teenagers who look like they could do with the exercise.
"The lifestyle here has changed so much in the space of a generation, the older guys are wiry but, for the younger ones, diabetes could become a real problem."
Football is well established - before the training session in the school, one boy asks Marsters if there is any money in playing rugby; local football clubs ferry kids to training, provide kit and even pocket money for the better players.
"So it's hard for us to get the most talented ones but they aren't all going to get into the soccer team and that's where the old line about rugby having a place for everyone is useful.
"The culture here is intensely proud. They thrive on a sense of identity - when the adults pull on a jersey for the national side, it just transforms them. It's a tribal thing. I guess we aren't so very different."
The UAE national team, who compete in the top tier of the Asian Five Nations (against Japan, Hong Kong, Kazakhstan and South Korea) is largely made up of expats but a quota system means at least two Emiratis have to be in both fifteens and sevens squads; an exclusively Emirati team, the Shaheen (Falcons), had their first outing at the Bangkok Sevens where they won the Shield.
"We're looking to fast-track guys out of the school system into international rugby, which is always going to be a challenge, and you have to keep a balance with the expats who are likely to make up the majority of the rugby-playing population for some time."
Sevens will be the main thrust for the Gulf area and the shorter format has a relatively long history in the Emirates with the first Dubai Sevens having taken place in 1970.
The event now draws crowds of up to 120,000 and those numbers hint at colossal potential.
The rise of the Asian middle class is opening up an interest in sport as a leisure activity across the continent and there's no lack of money for investment.
