Yes, it could be a symptom of something else, but getting motion sick is very common.
I had a lot of problems when I first started diving. (It seems to be mostly related to cold water - different subject) I would get ill sometimes on the boat ride out, and often I would feel really sick as soon as I surfaced. Some was related to the anxiety and some was related to being afraid to eat and some was related to the motion.
Usually I was fine under water, but at the surface I was a volcano, or struggling to keep from erupting. I have talked with a number of people and this seems relatively common.
I started using some of the over the counter motion sickness medications, and they were only marginally successful when taken as directed. When I asked around virtually all of the people I asked about it said the same thing: Ignore the directions; start taking Bonine or Dramamine a day ahead of time to get your system ready. I started following that advice and I have had far fewer problems.
Of course this is not "advice" and I am not a doctor, nor have I played one on TV, nor did I stay at a Holiday Inn Express. I am simply telling you what people told me, and what worked for me. YMMV.
Wristshot