I don't know how you can say for sure this is the worst cruise line ever, if you have only been on one ship.   We have been on several Carnival cruises and we never had a flooded room.   The Sensation looks like a pretty old ship.  Try some newer ones like the Carnival Splendor.  The Splendor was great.  Also the waiters and cabin steward gave us wonderful service.   What caused the flood?  Was the ship leaking or was it a just a stopped up shower drain.  Carnival ownes about 100 ships.   A ship is very complicated.  There is a lot of equipment on a ship.  It is possible that one day something could go wrong.  

That does not make the whole cruise line the worst cruise line ever.