Depends somewhat on where you sail from. If, for instance, you are sailing out of Palma or Barcelona then the sea will have less lumps in it than coming down through Biscay. What he might be forgetting is that in the Merchant Navy they have no stabilisers and believe me they make a big difference. Also the modern ships, especially the larger ones don't move around too much.
You can if you feel queasy get a tablet that helps and if you're really bad then pay for an injection and you will be right as rain in a few hours, but you never know you might be a better sailor than he is. Don't let him put you off the holiday of a lifetime...By the way we can give you a few years and some....Neil Dow.
My husband had great reservations regarding cruising as he is not a good traveller, but we are now coming up to our 15th cruise! Dont worry, ships are very stable these days, and if you do feel ill it can be easily sorted. Invest in a pair of wrist bands just in case and go and enjoy yourselves. Best wishes.
We have cruised several times from Southampton and can only recall really bad weather once, I think the best choice is to book mid ships as you do not get a lot of movement there we also have inside cabins so if it does get rough you do not have to see it. L benha.