I don't think it means you have a fetish, it's really easy for girls to get aroused wearing tight things that pull at the sensitive places and what-not. Always remember, fetish is nearly requiring something to be aroused- this is just a lil' case of accidentally getting turned on in a wetsuit.
It doesn't necessarily mean you have a fetish, sometimes it feels good to have something tight on your skin and it can turn you on a bit. I'm not saying you don't have one (and there's nothing wrong even in the slightest if you do) but it's probably unlikely. You could always experiment more if you want to, see if it's the same indoors with no one around. A common fetish is the idea of feeling "naked" but not being naked whilst in public, that with the tightness of the suit, could lead to you being turned on. Maybe try some tight fitting clothes on at home, see if it feels the same.