I also have the feeling of water running down my legs, its 1 of the many Parathesia like symptoms associated with so many problems its just impossible to list, the most likely cause is Anxiety in this case.
Parathesia is illnesses such as MS, is sometimes pins and needles, extreme itching or burning a stabbing pain in the face or in most cases numbness any the limbs or groin area. I believe you can also get a tightness around the trunk known as the MS hug, which is another form of MS parathesia.
Parathesia caused by Anxiety or BFS or from what I can gather Fibromyalgia or ME etc can be very different, and have all sorts of strange symptoms...like Creepy Crawly, Feeling of Water running, the Feeling like your Skin is stinging and can be sensitive to touch. Also medications can cause Parathesia, in paticular Anti Depressents cause this as a side effect quite commonly. Its not worth speculating but a bad cold can bring on a Post Viral problem that can cause Parathesia too, which is probably the culprit for a number of people on these boards. But after a recent discussion with my Neuro, the most common cause is usually Anxiety linked to Sub Concious Hyperventilating.
Hope this helped a little.