Large ships are typically launched into the water when the hulls are completed but that doesnt mean all of the construction work is finished Usually there is still a significant amount of work to be done including finishing the interior of the ship building the superstructure etc Take a look at ImageSMS Seydliz under constructionjpg for example you can see the ship is already in the water but a significant amount of work is being done to the superstructure You can also read Ship naming and launching for more information about launching Hope that helps