Another great animated short is La Maison en Petits Cubes
(The House of Small Cubes).
An old man lives by himself in a cubical apartment in a world of gradually rising water. As a result his home consists of one cube built on top of another. When he drops his favorite pipe he is forced to don diving gear and go down through the previous cubes that were once his home to recover it. On the way down he begins to recall memories - both happy and sad - of each stage of his life.
A lovely bittersweet parable about living and the process of aging. Captivating, dreamlike - and ultimately heartbreaking.
One of the best 12 minutes in animation.