"Water is a good, predictable process"

No, Waterfall is bad precisely because of the inherent unpredictability of a given project.

Never in all of history was a large software project speced out and built on time.

Software lives in a dynamic environment, so the process has to be mutable.

Maybe the answer is not 'Agile', but it's definitely 'agility'.

If we set longer term term, rounded goals, but with smaller iterations, then there's a possibility, but not a big Waterfall.