Actually it's a good one. Not one of the best, but still good.
This episodes was a nice addition to the show and added another layer to an already dark, eerie, breathtaking batman beyond universe. It showed us that even the sewers are scary/eerie and the things that are potentially hidden there. Also it gave us another glimpse at how massive the city is if even the sewers are like mini cities.
The atmosphere is pretty great and the episode is also pretty dark as well. The drama isn't bad either.