I believe when a cruise ship docks in a port there is a blanket VISA for its passenger list.The local government may not want too many people(two ships worth) out in town.It could potentially overwhelm the local area.Large ships have a strict schedule to keep.Docking permits,tugboat contracts and resupplies are all considered.Even tides on a deep draft vessel could cause a ship from docking for a couple of days til it can be scheduled.When a ships captain makes a decession to not let passengers off for a couple of hours it may be to save days later.....

BOATMAN
John