There are people prone to getting sea sick while onboard a ship and the more troublesome it gets when the ship departs from the port and getting fast at sea. It would be good if there are no large waves that will rock the ship but when it does, this is where the head starts spinning and then starts to throw up. You want to avoid the embarrassment unless you are inside your cabin doing this. For some people that were used to motion sickness but has gotten over it because of their consistent travel with the sea that they got used to the motion of the ship. The same thing can happen to you as well if you keep travelling but for the first few tries of your cruise trips, you will want to prevent motion sickness from happening when you board the ship.
Before boarding the ship, you need to get well rested, drink lots of liquid and avoid sitting backwards or putting yourself in a position against the motion while the ship is sailing and also avoid reading anything while boarding or doing activities that will require you to focus visually. You can also avoid getting seasick by staying away from places where the ship sways too much. When booking your cabin choose one at the lower deck either at the balcony or porthole in which it allows you to set your sight readily on a fixed horizon which will help set balance to yourself and to counter the effects of disorientation while being at the sea.
Avoid ships that are too old or has been sailing for too many years and choose one that has updated stabilization systems. Larger and latest vessels are equipped with such systems and booking a modern ship that will be taking routes through calm waters such as the one in the Gulf of Mexico will prove to be an enjoyable and smoother ride for you rather than choosing an itinerary that travels to the Antarctic. It is also a good idea to book an itinerary that focuses more on docking to ports as this will shorten your time on the sea and more on touring the land.
Medications to counter motion sickness will help as well and you can get OTC drugs like Dramamine or Bonine as this will prevent your sea sickness from happening. For those who suffer severe motion sickness, your doctor will recommend a stronger prescription for you.