Swingers cruise
We can only assume that a swingers cruise is basically a huge boat filled with couples who are willing to trade partners with strangers they meet on board. That sounds about right to us, we don’t think we would ever sign up for something like this, but to each their own.
Honestly, this kid shouldn’t feel so bad about what they discovered, what is the big deal here, your parents are experimenting and trying to keep the flame alive. Who knows, maybe they will return back home with big smiles on their faces and a stronger marriage. Or maybe not, it is risky after all.