How far apart can I place the anode and cathode when doing electrolysis of water?

Ever since I learned how to do electrolysis is high school I've always wondered how the oxygen and hydrogen manage to go so neatly into separate places once the water molecule gets broken up. Where are the molecules that get pulled apart? Between the nodes? At the nodes? How do the H2 and O2 molecules navigate to their respective poles to form bubbles? Ultimately...How far apart can I place the nodes and still be able to perform electrolysis? Does this affect the current required? Hmmm, I kinda just answered that last one in my head but still...please indulge me!