Okay, this post kind of fractalled into multiple conversation threads, thank you to everyone who participated! I learned a lot.
First, PVA, the skin of laundry pods, is a plastic. Yes, it dissolves in water (under selected conditions). But it doesn't go away. On this planet, there is no "away":
"Dissolve does not mean disappear. Salt is technically soluble in water, but if you pour a bunch of salt in a glass of water, you very much taste it. It’s still there."