But yesterday, the duo donned different hats - for treasure-hunting.
The pair were in Dunedin for the New Zealand Mega 2012 Cache In Trash Out (Cito) event in which international geocaching enthusiasts use GPS navigation devices to find containers, called geocaches, hidden in hundreds of spots around the city.
The caches contain logs of geocachers' codes, or items for trading.
Essentially, it's a high-tech game of hide-and-seek.
Mr Swennen and Mr Vetter said they had travelled the world for geocaching events, but insisted their enthusiasm for treasure-hunting was just a hobby, albeit a very expensive one.
They were among geocachers from as far away as Australia, Latvia, Denmark and the United States.
As part of the event, participants were expected to pick up any rubbish lying about the city while they searched for hidden geocached items.
And yesterday, Dunedin's Octagon became a temporary rubbish collection site when about 300 geocaching enthusiasts zeroed in on the landmark to show how much litter they had gathered during the three-day event.
About 50 bags of rubbish were later removed by a refuse collection truck.
"It's fun," Mr Swennen said.
"And also, helping to clean up the environment is a bonus.
"You can do your hobby and participate in something good."
