cliffpatte
Speed camera anarchist
Water neutralises the developer by diluting it to the point where it is no longer effective. You then rinse it away with a second wash. No development time is that critical; not even colour. Just don't leave it sat for ages before you put the fixer in.
I think there is a bit more to it than this. If you use full strngth developer and a short development time then the time required to stop can be significant. Also if you don't succesfully remove the developer before hitting the fixer it will reduce the amount of times you can re-use the fixer - frankly since it costs very little, I am happy to spend the extra bit for the peace of mind.
more on this on a flickr group here