On a very hot summer day in Tomobiki town, Lum, Ataru, and the rest of the gang are looking forward to using the school's pool. But the teachers have other plans: setting a ludicrous obstacle course between the students in their swimsuits and the pool... naturally this ends in complete chaos.

— written by foo2

Note: This special tells the story from manga volume 23. It was originally exclusively screened during the "It's a Rumic World" art exhibit held in Tokyo's Ginza district from July 30 to August 11, 2008 together with two other specials for Inuyasha and Ranma 1/2. On January 29, 2010 a limited edition "It's a Rumic World Special Anime Box" DVD collection was released which contains all three specials.

AniDB | MAL | TVDB

Parent story: Urusei Yatsura