For clarity's sake: I didn't find out these things myself. All the research was done by my greatuncle Cees (Cornelis), his son Gerard and my (rather remote) uncle Huib Bongers.
De Waa is small lake near (or, nowadays, even in) Hattem (a small town, south of the Dutch city of Zwolle).
Apparently, this is the origin of all people calling themselves Van de(r) Waa, but the relations between them are none too straightforward. There are at least three interrelated branches, but there seems to be no common male or female ancestor.
I've added this English introduction mainly for the benefit of our American relatives, who may have some difficulty with the Dutch language.
The core of the Van der Waa Genealogy consists of more than 150 interconnected "family pages" by which you can browse through the family tree. They can be accessed via the register, a complete index of all known ancestors and descendants.
For better insight, there is a compressed family tree.
Furthermore, I added my own ancestry line, to help find out common ancestors.
Recently, I stumbled upon a curious family line, which leads all the way back to Charlemagne (Karel de Grote) - for what it's worth...
If you need more translations, or want to receive or add extra information, I will be only be too glad to receive your e-mail.