The shower pan was filling up FAST. In this photo, it's about 1/2" deep, but it'll just keep filling up if I let it run longer.
Going at it with a zip tool got the drain to, well, drain.
But when I tested it, the drain filled up again. So removed the drain cover and brought out the big gun: my manual auger. And this terrifying creature came out. My wife said we should name it.
After a second test, it drains! No more standing water.