The Water Supply is a large area with a big red machine located near the right side. the previously mentioned machine gives water to the Hydro Generator, allowing it to create electricity.
During B-1: A Job for a Plumber, Luigi must go to the Water Supply to get the Hydro Generator to work. However, when he does get to the Water Supply, a Greenie wearing a bucket as a protective helmet attacks him. After managing to defeat the Greenie, Luigi must fill the bucket with slime that is coming out of the pipes. There is a switch that must be weighed down, so Luigi must place the bucket on the switch. Now the Water Supply can be activated once more. Unfortunently, after activating the machine and getting the water to flow once more. the water goes through the slime-ridden pipe, and it pumps out a large clog in the machine. As it turns out, the clog was a Gobber. This would be the first encounter with a Gobber, unless the player encountered one in a ScareScraper game. Once the Gobber is defeated, the mission is complete. After this mission, there is nothing else of interest in the Water Supply.