Yup, happens all the time. Well maybe not to the point of feeling sick, but the floating feeling happens. Give it a couple of days. Your body is used to the ship movement and is still trying to compensate for it.
The only other solution is to book another cruise and get right back on! But that only postpones the having to get over it part...
Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise
NCL Dream October 2006, RCCL Mariner OTS June 2007