I’m sure there are also circles where less-clothed social events do happen where not everyone at the event is already mutually acquainted. While I’ve never been to those event myself and haven’t be told the social protocols explicitly, I would assume that if you aren’t crashing the event, you are allowed to speak to less-clothed persons you’ve not met before, to introduce yourself at least.

(I’m not a pretty person, so I think I’d be even more uncomfortable that such events than I am at other social events.)