Perhaps the late tourists would want to pay the penalties & fees for failing to vacate the dock on time.
When you book a tour with a private tour company, not only do you risk missing the boat, but you never know the quality of the tour.
We booked a private snorkeling tour in the Bahamas. On the boat trip out they served rum punch in plastic cups. It was good, the snorkeling was fun. On the way back to the ship, we noticed the deck hand taking used cups out of the trash for more rum punch. He didn’t wash them. We declined. Yuk!
You may pay more for a ship-sponsored excursion, but the cruise line guarantees the ship will be there when you return to the dock & they vouch for the quality of the tour company. When you are thousands of miles from home it is best to stick with things you know & trust.
IF the Rum was high enough proof, it would kill the gems anyway!
:)