@MikeMason-- I guess you had a lot of water retention because it's not possible to lose weight (fat) on diuretics. I'm sure you have been urinating more frequently since you started the medication right?
If you were to stop taking it, you would start retaining water again and eventually return to your prior weight. I'm also guessing that at some point, after all the retained water is gone, you will not lose any more weight on the diuretics.
I understand you have to take these medications for health reasons. But for those of us who don't need to take it, following a water retention diet which reduces salt intake or having a few cups of green tea is enough to reduce water weight.