A vascular surgeon can also dx & treat NTOS I believe.. they aren’t limited to Vascular issues only..

So you had a concussion or possible TBI from the pool diving? You hit your head?
That can cause quite a few issues also..
If so you might benefit from some upper cervical chiropractic care.. it is not scary, if you are leery of general chiropractic the upper cervical is so gentle. look it up on you tube.. but basically your c 1 c 2 probably got really misaligned when you hit your head in the pool..
info-
www.upcspine.com
http://www.upcspine.com/self.htm

A full cervical MRI should be done as mentioned..to clearly rule in/out any injury.

Have you had any expert PT at all?
They can do some positional & other testing during the evaluation..