The Magic currently has an extensive water leak problem that runs ship-wide. The main purpose of dry dock is to fix the plumbing and repair damage caused by water leaks. I only know this because we just sailed on 2/15 and we could feel water squishing around under our feet in the bathroom. The water wasn't visible and the floor was dry but when we talked to our stateroom steward about it, he said that the problem was extensive. We assumed we were the only ones dealing with it since we were on deck one but we talked to people as high as deck 7 experiencing the same thing. Sorry!
Sorry, but the main purpose of a drydock, especially this one is to satisfy MSC/IMO/SOLAS regulations. The way it works is that a ship is mandated to go into a dry dock, 2x in a 5 year period, not to exceed 3 years. Magics last drydock was in Sept/Oct of 2010.(I was on her first post DD cruise) If she doesnt make it, or the yard runs late on the ship infront, the Magics hull certificates etc will expire, and she wont be able to sail until she goes into the dry dock for inspections. The purpose is to inspect all of the areas, that cannot not be inspected while in service, such as fuel bunkers, sewage tanks, water tanks, thru hulls, running gear etc. At the same time, the MSC most likely will have made changes to different things that may be coming up on a deadline. Things like the amount of flammable materials onboard, or amount of a certain type of paint, fire protection changes etc. Any or all of the above can put a ship out of service, if the change is serious enough and not corrected by the deadline.
While shes there,
DCL (or any line for that matter) will take the oppurtunity to work on areas, that can not be easily worked on while the ship is in service. Things like the persistent water leak, renewing or replacing kitchens in their entirety,(The Magic got a ships laundry room upgrade in 2010) renewing a mdr or completely redoing a pool(s).
Things that can be done while inservice, like bed changes or linen changes usually are, but depending on the supplier, sometimes its easier to wait on a drydock. If you ever get the chance to see Extreme Cruis ships Oasis of the Seas, they show where she comes into port, and a large number of crew remove and replace a few hundred mattresses that wore out prematurely, prior to guest boarding. Basically as a guest left their rooms, several crew members went in, grabbed the matresses, and went to the loading doors with them and offloaded them. The stevedores bought the brand new ones to the doors, and the crew reversed the process.