We were on a cruise with another couple. Just regular friends, our age, absolutely no sex play had or has ever happened.
Going into dinner one night we playfully swapped wives on our arms as we walked to our table. The looks from others nearby were unbelievable. (Everyone sits at the same tables every night throughout the cruise so you kinda know who sits where.)
One woman quietly and politely asked the wife of our friends if we were swingers. She jokingly answered she wished we were.
Nothing came of it, it was kinda scary but was fun.