Lower deck, midship, is the most stable area on the ship. This is one of the main reasons that many of the medical centers are in this area.
One thing to remember about Bonine (Meclizine) is that it is a preventative and should be taken BEFORE you become seasick.
Take it on a daily basis. In the evening is best in the event you are one of the people that Meclizine makes drowsy. Once you are sick it won't help one bit, and as Paul "shared", you will probably give it to the porcelain convenience.