I have been on 3 cruises, with one of them going out of NY. Now mind you....I get VERY sick sea....very sensitive with motion. Anyway, with that cruise (which was our first) we went to the Bahamas and Bermuda. First day, I was fine. Next morning, we went to one of the restaurants which was in the very back of the boat and the whole back wall was windows. First mistake I did was look out the window and saw the water waving back and forth (not a lot, but enough to make me a bit off...a little dizzy) Needless to say, I went back to my room and slept on & off all day.
I finally took some dramamine and was fine the rest of the week. We did fall in love with cruising and I found that if you take the dramamine THE NIGHT BEFORE you even get on the ship, you'll be absolutely fine. It needs to get in your system before you get sick and it'll work that much better. Than you take one each morning. Easy Peasy!!!
That was in 2006. Then in 2008, we took a
Disney Cruise with friends of ours to St. Maarten & St. Thomas. That one left out of Port Canaveral. The motion of the sea was fine except one night/following morning. We were sitting in the dining room that night and kept feeling the boat sway from one side to the next and some of the dishes on the tables falling off.

That night happened to be A LITTLE much for me. Not too bad but I told my friend to watch my boys so I could go out on deck to get some fresh air. Once I did, I was fine. Was actually watching the front of the ship come way out of the water, up over the waves. It was actually pretty cool. That was the only rough seas we had that trip. And then last year, after a weeks vacation at Disneyworld, we decided to do a 5-night cruise out of Port Canaveral again. This time, just to Nassau. This cruise was perfectly still. Nice & calm. We are taking another cruise in July of this year and we're leaving out of NY again. (We live in CT, so it's much closer and we don't to buy airfaire, so it's much cheaper) Going back to Nassau (not the we love this island, cause we don't LOL but we do love Norwegian Cruise Line's private island!!!)
Sorry for the long winded post. But I thought I'd give you a perspective on what I've experienced. Like I said, a cruise is so much fun. So if you're prone to motion sickness, just pop a dramamine (or bonine, can find both at
Walmart) the night before you leave and you should be fine. Just make sure to continue taking it each morning.
Happy Cruising!!!