I would be inclined to make life simple and non-demanding for her in terms of getting used to new things or new places or too many changes of scene in one day. What I suppose I am trying to say is, that intellectual development and emotional development don't always go hand in hand, so she may appear very advanced in some ways, but may still need to be babied in others.
My NT daughter liked to be in a pushchair when she was 4.5 years; she felt safer on journeys, and hated walking long distances, although extremely athletic and active in other ways. People told me it was babyish, but if she needed it..then it was what she needed. At 5 she wouldn't have wanted to go in a pushchair because it wasn't cool!
A lot of small children may find swimming pools very overwhelming, without any long term problems. I would be guided by her. If she doesn't want to go swimming now at tender age of 30 months, try again when she is a bit older, you may find it is the right time.
Disclaimer: I have two children with sensory needs, one with ASD, and I think it is a question of adapting to what child needs and see how it goes over next year or two, rather than feeling there is a big difficulty now, and getting stressed by it. Your input now, at home, to make her feel safe, will be better than anything professionals can offer you. Try reading Out of Synch Child and Out of Synch Child has fun for some ideas.