Chalk up another "I didn't know that" life moment.
As you can see in the first picture below, there was a nasty buildup of "green slime" at the bottom of our shower door. After several rounds of my wife trying and failing to eliminate the goo, I finally wondered what was going on and found there is a removable plastic track (thanks YouTube!) at the bottom. I found a replacement at the Lowes link below, cut it to fit, and the unsightly mess is gone.
I'm now in the running for "husband of the year".