If the ship docks at 6.30am then everyone will be off by 9.30am latest - they have to clean the ship and get her restocked before the new people get on at midday. As you do not say what cruiseline or what port we cannot offer advise as to what to do during the day....
You will probably be the last one off if your flight is late on & the latest for any passangers, but it will not be late in real terms if the ship has a quick turnaround & is embarking passengers for a sailing that night, so you could expect to be off by 11am at the very latest.
Depends on the individual cruise line, bit generally they want you off early Some want you out your cabin at 8.00am others 7.00am. They usually start disembarking passengers very shortly after that. It also depnds on whether or not they are providing you with a transfer to the airport or not. If they have they will want you to be off the ship to fit in with the time the coach is scheduled to leave. Other options to pass the time other than spend ages at the airport are, if yiu like organised shore excusrsions, the n the ships often have tours you can go on the day of disembarkation that will organise storage of your luggage and then take you to the airport at the end of the tour. For example if you are disembarking at Port Lauderdale and flying back from Miami, they will probably offer trips such as Miami City Tours with or without shopping time, trips to the Everglades and so on. Other alternatives are to use luggage storage at the port or airport or go off and do your own thing. Sometimes the cruise line will offer this too. Contact the cruise line you are booked with and they will be able to tell you what to expect and what your options are.
Generally the ship leaves around 5-30pm and most will allow you to stay on the ship until the last minute we have never had any problem with late flights and being told to get off early.
You could consider doing what we are for our Feb cruise, we have a late flight from Miami back to UK @ 5pm we have booked excursion to the everglades and sightseeing Miami from 8am to 1pm well worth the money £35 each .