When I was single and traveling solo, I would do a "walk by" wherever the get together was being held, and depending on what the crowd looked like I would decide whether to go in or not.
As has been mentioned above, depending on the demographic of people on that particular sailing it happened to be a lot of fun, and I made some friends I got to hang out with during the rest of the cruise, or I didn't meet anybody in that event, and ended up finding people with similar interests in other activities throughout the week.