The S.S. Indulgence is a yacht bought by the Jefferson County Middle School board and is used as an explanation for the school's shortage of funds in Acadecamathalon and The Math Book. The students visit the ship in Some Like it Yacht.
In Some Like it Yacht, the faculty use it to bring the students on a field trip. They ended up on a tropical island like in Swiss Family Robinson. After Diogee helped Milo find a way back to town, the boat wins a surf contest via loophole. The prize money from the was then used to fix the damages done to the boat when it crashed with two dollars to spare.