It's mostly seeping underneath I think. Nonetheless, the water is back up about 2" this morning after I just absolutely loaded it up with with clay and rocks, so at least the fish genocide seems to be averted for now. Getting some quotes this weekend on having it done the right way.
It's all good. There are a lot of folks who have much bigger problems than leaky bass ponds and nettlesome swimming pools. If those are my big sorrows for 2020, I'll be in a pretty good spot.