It's down to the prevailing weather and sea conditions the route the ship is taking against the current of the sea, and the hight if the waves and the stabilisers use and ballast weight.
This is the best article there is.
http://traveltips.usatoday.com/prevent-motion-sickness-cruise-1777.html
Dream and Fantasy are new ships with latest technology and fully stablized and has special paint on the hull to allow it to glide in the water.
Ships captains will do thier best to avoid bad weather so the risk of sny sickness is minimal whatever deck you are on.
Now the " low" is best is a myth posted around by a few posters.
Ask yourself simple science questions to get the correct answer.
- Where in the ship is the sea next to and where are the engines?
- What part of the ship hits the water first.
- Where would vibrations from the engines be the worst?
- Where in the ship would vibration from the waves be at there worst.
- If someone is claustrophobic where on the ship is the best and worst places ?
this article is written by people who study this and what they say.
Sea sickness is caused when your ears detect movement but your eyes say walls do not move, to correct it you need fresh air snd look at the horizon at the widest point.
You do "Not" want to be near the vibration of the sea, or the engines, and you need fresh air not pumped air.
All decks are joined together but the ship will flex in the water, so that it doesn't "snap" like tall buildings they do move.
A lot depends on so many variables you can't get an exact answer, waves, -different types and height, ship direction ,to sea direction, to current, wind, and if ballast is taken on.
If top deck right moves right, bottom deck left can move left.
What we do know is very very forward where a ship cuts into waves is the worst, it takes the energy from them, bottom decks get a lot of small movement due to waves, this is ironed out to a Gentle wave the higher you go, do you see the water in the pools on the top decksrock slightly with a slight wave one way then a return.
My daughter gets bad motion sickness and seasickness, it's worst on small tender boats that are low in the water and enclosed. We have sailed on
DCL through the back end of Two hurricanes and one severe storm in the Med. The best place was our room deck 8, she couldn't eat in the restaurants on the lower decks but could have room service in our rooms.
If anyone has seen the dancers and performers trying to do a show in the WDW when it's rough, they will know exactly where the movement is, very funny to see a jugular try to do his act in tough seas with a tennis ball, axe and bowling ball and it keeps moving.
For those who say low is best, where do you spend most of your day? The pools and slides and sun beds are on top of the ship, so why say low is best if then to stay on top deck all day and it's ok?
If the top decks were bad the water would run out of the pools.
With motion sickness say in a car, the driver doesn't get sick, but if your not driving and reading you can get that sick feeling? Well same on the ship, in an inside room, ears note we are moving, eyes say walls can't move, so give the old brain some information concentrate on the horizon and unless you have an underlying Heath condition then it will correct itself.
So to be safe, get a midship, mid deck room, and with a verandah if you can. Get fresh air, drink light with water avoid fatty food, yes I know it's a cruise, we all do it.
I have been to the medical centre which is forward and low, doctors have said it's built in the worst place for movement, I have spoken to ships engineers who disagree with low is best. They say it depends on do many things.
The price of a room goes up the higher you are up a ship, if there bad for seasickness would that be the case?
It's not tradition ( it's not buying antiques) it's because people pay for value.
Finally if DCL opened up 2015 summer say on Monday week and said all rooms ( bar concierge) are the same price, what would everyone here books. I have never read of anyone refusing an upgrade to a higher deck room or verandah.