Good points made. When excursions are reserved through the cruise line itself, they try to schedule tender departures so that people make their connection. Same for return to ship. If the cruiseline-arranged excursion is delayed in getting back to the ship, the ship won't leave until those passengers get back on board. We had an experience in Barcelona like this and thankfully were able to relax despite the bus breakdown because it was an "official" excursion.