I really like this train of thought Marly. And you are totally right. reality and dreams and the line in between is very slippery, who knows what is real or not or what is more valid as an experience.
I find it very interesting you had an experience like this while surfing. Action sports (physical activity that brings you very much into the present moment) can alter your brain activity and completely change your state of consciousness, much like other consciousness altering activities (trance dance, psychedelic substances) allowing us to either activate or shut down certain areas of our brain allowing for altered states.
Flow/Zen is and amazing state of consciousness that is not understood nearly enough. Luckily there are some people looking into it. Checkout the flow genome project http://www.flowgenomeproject.com/
Some amazing people doing scientific research on the benefits of these states of consciousness, much like you experienced.
Thank you so much for sharing, its great food for thought and will have me thinking all day!
Keep up the good work.