I'm guessing all the books in the purchase area would apply to a 50 acre pond. I would just have to multiply everything? Because I just ordered 5 books from here.
That is an awful lot of man-made private water -- especially new water. Being in Ewa, look across to Hospital Point, and try to envision how many 50-acre parcels you see.
I certainly don't ever want to dampen dreams. But, if you want that much private water, think about buying a large farm in a place like Northern Minnesota, Northern Wisconsin, Upper Michigan, in-land Maine, or in parts of Manitoba. There is a good chance you might be able to buy a lake of that size, or at least one with just a couple of owners. Excavation, a dam, drainage, and permitting for a lake of that size will not be inexpensive.
Let us know a little more about what your are planning.
Ken