Yes, indeed: competitive frisbee. The game is sort of like netball, in that it is non-contact and the person with the frisbee can't run with it — only pass it to a teammate — and also sort of like gridiron, because you score by getting the frisbee to a teammate in the endzone and that the idea in general play is to gradually make yardage up the field as you have possession.
The sport surprised me in a number of ways. Firstly, the higher-seeded matches displayed a great deal of skill: those guys can really throw with speed and accuracy and have superb control, when it's needed, over the way the frisbee swings to the left or right; and they were quite competitive as well: teams made a lot of noise when they scored and there was fierce support from the sidelines as games were on. And secondly, the lower-seeded matches were much less skillful: the participants were clearly just having a pleasant little run about in the park with their mates. I knew it was an amateur sport but at rare times I found the national championships just a little bit surprisingly amateur.
My task was simply to assist the organising committee with whatever was needed to aid the players. I helped prepare the lunches, man the bar, keep the bins empty and the water barrels full and also just point at stuff for people — all your standard volunteery things. They gave me a T-shirt.
The kicker was that I went five days straight without email and internet! How I am still breathing, I don't know.