I've only been on one cruise, the Wonder, and they had it in the Oceaneer's Lab (I wasn't old enough at the time for the teen club). Just about everyone played and loved it.
I can be bad at wording things out for others to understand, so here's a site page that explains it fairly well:
You're in a circular sort of ring, the floor is covered in sand, and you hit the ball around. You can't throw it, hit it out, or kick it. You try to hit everyone else anywhere below the knees. If you get hit below the knees, you're out. The game ends when there's only one person left. That's about it, I've only played it at camp a few times.