Get Earplanes Earplugs to equalize the ear pressure on the airplane. They work perfectly! You can get them at CVS or Target (ask the pharmacist). If they are out of them, you can ask them to order them. Make sure you take extras in case one falls out and gets lost on the plane of the floor.
Use Benadryl for motion sickness. Just ask your doctor to make sure you give the right dose. It has the same active ingredient as motion sickness pills but comes in the right dose for 1 yr olds. I would give it to your baby no matter what. Most people seem to get motion sickness on ships and it is much easier to prevent than to cure. Once you get sick, it takes a long time to get over it.
For bathing, you should either bring an inflatable bathtub or just hold your baby in the shower. The shower heads usually can be lowered to waist level, so that makes it easier to shower your baby, but you do have to worry about slippery babies then. We showered our 4 month old and 2 yr. old without any problems, though.
If your baby is walking please remember, ships are not childproof!! They CAN fit through railings that face the interior of the ship (as in fall through to a lower level). I would keep a hand on her at all times. And frankly, even if you think they are creepy, a cruise ship would be a good place for a baby leash. Ships are very busy and crowded at peak times of the day, even more so than a mall.
Don't forget, you can't get diapers/formula/etc. on a ship. If you don't want to take it on the plane, just use the hotel shuttle to make a grocery shopping trip the night before your departure. That's what we always do. By the way, bringing your own sodas is a good way to save money since you have to pay for it on the ship.
If you didn't already plan on it, make sure you spend the night at the port of departure. NEVER arrive by plane on the day your ship leaves. If your plane is late or cancelled OR IF THEY LOSE YOUR LUGGAGE (which happens all the time) you have major problems.
Have fun. I wish I was going!