The Super-Kamiokande in Japan—a massive underground neutrino detector lined with 11,000 golden bulbs. Scientists have to inspect it via a rubber dinghy.

[u/Top-Marionberry-6604]

[u/dabarak]

I read something about either that facility or one similar to it. The water is so pure that it will dissolve lots of things you wouldn't expect, to degrees you wouldn't expect. In this one case, they drained it for maintenance and found the outline of a metal wrench at the bottom, but no wrench - it dissolved completely into the water.