Loved the size of the ship - would NOT have wanted a smaller ship with the waves and the boat movement. We did nothing to avoid sea-sickness (no patches or medicines) and had no problems, but I am glad the ship had stabilizers. Be sure you do a BRIDGE TOUR; this was the best such tour I've ever been on, most informative.
We brought only a small carry-on and a backpack apiece so nothing had to be checked on the flight to and from Quito. We had plenty of clothes. Brought only shorts and shirts, one pair of long pants for Quito and a rain jacket; everything was very informal. Took a pair of water shoes and our Sketchers SHAPEUPS. The Sketchers were THE best for walking on the lava. Did bring our skins and were extremely happy that we did. We did not use the wetsuits that the ship provided at all. The skins kept us plenty warm and were much more convenient than the wetsuits. We did ALL of the snorkel trips available. We are accustomed to our own fins but used theirs and were happy enough. We did bring our own masks and snorkels, however. Brought a small notebook computer to download pictures each night.
Be sure to say "hello" to the Captain; he is extremely pleasant and no one talks to him. He enjoys talking to passengers.
Try to watch the National Geo series on the Galapagos BEFORE you go, if possible. They show it on Nat Geo WILD often. You will recognize the birds, lizards, etc when you see them.
The crew was fantastic - very helpful. Best food ever - lobster 5 times. THE best desserts. I usually don't eat dessert, but these were a perfect small size and were delicious. Naturalists were so well-prepared, friendly, and helpful. They led discussions on life on the Galapagos, geology. Took pictures throughout the trip and presented us a CD at the end of the cruise. The Cruise Director was very informative and caring about the safety of all of us.
The hotel in Quito was lovely, full of roses. Nice stay there. Celebrity had everything on land well-organized so everything went smoothly. The restaurant was delicious - Carmines.
The entire cruise was flawless with respect to Celebrity's involvement. Can think of nothing negative to report. Kudos to Celebrity.