At Sea in Zih

Last year we cruised from Miami to Sydney, Australia, on the Seven Seas Mariner, and there were 1200 passenger on board this fine vessel.
We had a wonderful 66 days aboard, and even though we were unable to go to 3 of the scheduled stops, due to inclement weather, it was a wonderful trip.
Rob is quite correct stating that different countries have different understandings of the terms 'Ship'and Boat.
Having worked on cruise ships for several years in the '70's it is normal, in British-English, to call any vessel that can be 'CARRIED' on a Ship, a Boat(in the merchant navy), however, the only 'boats' in the Royal Navy are - submarines. The US mercantile marine may differ.