As predicted, the first fruit burst and these were floating on the surface of the pond. I gathered them up, which was a bit tricky around the prickly leaves, and I'm trying to figure out whether to clean them before sentencing them to the refrigerator. Apparently they're edible as well, though I might be better off cutting the fruit off before it bursts so that the nuts are more tender...
For my own reference and reassurance of viability, I'm going to try germinating a few, although I don't plan to grow them out again until next spring.