RAH,
Was the pond still full when you were trying to perform that work, or would you had to have dealt with quicksand regardless, due to "outside" groundwater also saturating your sand?
I am hoping the OP can re-fill his pond this fall and pinpoint the location of the leak. Hopefully, that would make it fixable within his budget, unless your experience indicates that even the "small" fix might require big work to accomplish.
