I get a bit claustrophobic when I am in large crowds. I wouldn't characterize my issue as anywhere near what you describe, but I do get anxious and have to calm myself down. The only time I felt uncomfortable on the Celebration was when we were getting off the ship in one of the ports, and everyone was trying to get off the ship at the same time using only one route. It took about 45 minutes, and we were all backed up in a stairwell. I would recommend waiting to get off the ship until the initial crowd dies down. I have rarely had issues with crowds at embarkation. I try to be one of the first onboard to get to the food before the crowds arrive. Even so, I strongly recommend finding an alternative place to get lunch the first day, do not go to the buffet that can get very crowded very quickly. Personally, I like the deli on day 1. I loved that on such a big ship the crowds were spread out and it was easy to find a quiet corner to relax and people watch. Have a wonderful time!