Two liquid facts to put next to each other:

1. On an average day, the gross quantity of interbank transfers is $4 trillion. (from voxeu).

2. Assuming a drop of water is 0.025 ml or 25 micrograms, it would then take 10 olympic size swimming pools to hold 1 trillion drops of water. (from Wikipedia).

Also: "Finally, note the rather amazing fact that during normal times the banking system uses $12 billion to engage in $4 trillion in daily transactions. That is, on average a dollar in a reserve account is used more than 300 times PER DAY."

From voxeu again... Yikes. I have absolutely zero idea what any of this really means.