I have been in a "group grope" three times - a group of naked people in a pitch dark room, no talking allowed, the floor covered with mattresses, where anything can happen as long as the other person you are in contact with consents, and it was a fantastic and liberating experience.
The groups were from 20 - 30 people of different ages (above 18), an equal number of men and women. In a pitch dark room so you have no idea who is groping you or who you are groping. I was groped by several women at the same time, by men occasionally, I had sex with several girls, all in the time of 30 minutes.
When the lights went on after 30 minutes, everybody had a big smile on their face.