As mentioned earlier, the cruise is (depending on your outlook) a bit long, however, when the boat comes back around for the last time, you can often take the little dinghy back ahead of schedule. If you let them know (in the nicest of ways) that you're not up to the rest of the evening (as in perhaps turning green from the journey, or green from the alcohol consumption, or green from...?), often the crew can and will accomodate you and give you a lift back to reality....
oops, I meant dry land.
Lotsa fun if it's your trip, not so much if you'd rather not be there.
A dinner outing.... uh, no.
Not by any means.