Modern air travel is an extraordinary complex system. The endless series of arrivals and departures at any large airport is a carefully choreographed dance. Unfortunately this system can be easily snarled when the process is disturbed.
Next problem? No gate was available and we spend 45 minutes sitting on a taxiway waiting our turn at a gate for disembarking. I have plenty of time to observe that puddled water and the low slung engines of a 737 can create fascinating little vortexes of swirling water just below the engine intake. We were not worried, we had a five hour layover in our schedule and being late to the gate was not an issue. Many of our fellow passengers were not quite so relaxed, fretting about tight connections and missed flights.