Keep a healthy diet and avoid alcohol
Try to avoid unhealthy diet while on a cruise ship. It is always good to avoid acidic or spicy foods during the journey as this sort of a diet can cause seas sickness. You would want to enjoy the time you spend in travelling so being healthy and fit should be a major priority.
Take proper medication
There are medications that help avoid sea sickness. Medicines such as Dramamine and Antivert are very good in helping you overcome any illness during a journey by sea. It is always helpful if you keep a specific amount of medication with you while you travel. Make sure to consult the doctor before you use any such medication and ask him what quantity best suits you.
Get fresh air after regular intervals
Sitting inside can cause nausea and uneasiness so it is always good to spend some time outside and get a breath of fresh air every once in a while. This will help you keep fresh and active during the journey. Whenever you feel a hint of nausea or a sick stomach, the first thing you should do is to stand outside in the balcony or on the deck.
Avoid activities that may cause motion sickness
Try to remain active and avoid lying down for a longer period of time. Avoid any such activities that may cause motion sickness like reading a book and watching TV. It is always good to do something that keeps you engaged so that the slightest of feeling of nausea does not cross your mind.