There have been numerous "special group" events among charter travel providers where nudity is just one of the "common interests" of the groups. If you're a member of such a group, it appears to be common enough that you'd have heard of at least a few.

Publicity is usually "discreetly limited" to members and fellow travelers, but I've seen (but not received, ^#$%@) invitations to "nude cruises" with an entire (small) cruise ship reserved for such group plans.

A trip of this kind really isn't more strange or less usual than a local church making a "members only" trip on a bus. (Or much less bizare/perverted(?) than a bunch of fans going to a foootball game together.)

A coworker, ca 1967, reported at the office one Monday morning ca 1967 that a dozen members of his sky-diving club had performed a nude "demonstration jump" into a nudist camp in Michigan the previous weekend. (His most memorable comment was "those straps HURT!") Their inquiry to Guiness as to whether that was a "new record" got the reply "been done too many times."

John