You don't say if you are cruising to and from the UK, OR flying out to the Caribbean for a cruise. It really does make a difference as to, 'the motion of the ocean'. and also what time of year.To and from the UK you may get some rough weather before the Azores for a few days and the same on your return. IT may be great though.After the Azores each day gets warmer until the Caribbean as the ship takes a southerly route and not the North Atlantic route towards New York.We have done the Caribbean in winter many times but always without flying, just by ship.
If you are flying out to join your ship in the Caribbean then the distances between islands are small and the weather is always good, except for the hurricane season which you should avoid. We love cruising and have done almost 400 nights at sea, loving every day of it. Thankfully neither us us suffer from seasickness but our neurologist said that Stugeron, even though the information leaflet advised against it if you are taking certain Parkinsons meds,is fine on a short term basis, Do check though with your neurologist.
Have a great cruise. Your first will definitely not be your last..... it's addictive and a great way to travel.