It depends upon how you define "nudist" group. My first wife's family were a bunch of nudists. I was soon baring all -- which admittedly ain't much -- for her mom, pop and brother at their nudist camp/resort. Nothing sexual went on there, unless you include roving eyes and boobs and cocks on display.
But we'd occasionally take our show to an unsanctioned, hippie-like nudist commune. There a lot went on besides what went off. Mostly off the beaten paths. Behind every bush there was often a bush being beaten. One of them, my wife's.
Nude beaches often had secluded areas where a lot came off and went on, too. Private au natural gatherings could also vary in the degrees of hanky-panky allowed.
It's how you define your terms and where you go. If you're talking about family-oriented nudist parks, not much. If you're talking gay baths, a lot -- or so I've heard.