To save you, the reader, from the trouble of clicking through the Schlock Mercenary archives just to find strips detailing the last time Schlock was in a sewer, we've thoughtfully provided the following links:

Schlock helped Kevyn place some sensors in the "Big Haunted Battleship" storyline. He also got put in a ship's sewer by well-meaning commanding officers during the "BOARDERS!" storyline.

Then there was this one time with the circus, but you'll have to wait for the associated flash-back for that choice bit of scatalogical entertainment, as well as the answer to the question "How big a toilet bowl do you need to keep a sentient circus elephant happy?"