Is it normal to retain water after Breast Augmentation?

It is normal to retain fluid after a surgical procedure.   It varies by individual, but some retain very little and some retain quite a lot.  Most of the time the problem resolves spontaneously but occasionally the kidneys must be nudged a little and a diuretic is prescribed.  You say you have taken "water pills".  If they were over the counter, then you will need a prescription medication.  If you already have a prescribed medication, then you will need a higher dose.  Check with your surgeon.  Good luck.