I often go on that Community Board and ask to join a cruise. Over the years, I probably have joined in 8 fireworks cruises in that way. Only once did we book the cruise, the other times we joined a group. This has been for Illuminations as well as Wishes.
So, go there and ask, you never know!
Only once did I and my friends show up, and the originator of the thread did not show up. We were disappointed, but nothing really lost.
Bobbi