I would suggest taking a tour from the ship excursions. It might be a bit more expensive, but if there are any problems encountered during your tour, the ship will wait for you. If you choose to do your own tour, you are on your own and if you do not get back in time for any reason , the ship will sail without you. Then it becomes very expensive as you have to fly on your own dime to catch the ship at the next port. I have been on the ship many times and while sailing away I have seen people running to get to the ship only to realize it was away from the dock and on its way!