The Beach Bum is a spiritual sequel to The Big Lebowski, and while it's so light it's practically gaseous, at least it's not mean-spirited and immoral like The Jesus Rolls. The movie works, insofar as it does, thanks to Matthew McConaughey; his character is best described as a Southern Dude, and McConaughey is arguably the only actor capable of playing this role in a way that isn't imitation, parody, or even homage, but as a parallel entity, independent and original (it doesn’t hurt either to have strong supporting cast that includes Snoop Dogg, Jonah Hill, and Martin Lawrence).
There's a reason to watch this film written and directed by Harmony Korine, and it's called escapism. The plot, such as it is, follows stoner poet Moondog’s adventures in and around the Florida Keys, which involve copious amounts of sex, drugs, and alcohol.
Moondog is never hungover (presumably because he’s always more or less intoxicated), has no use for money, makes friends everywhere he goes, and generally always lands on his feet; as Moondog himself puts it, "I'm pretty sure the world is conspiring to make me happy." In the end there is no resolution because there was never really a conflict in the first place; the film is the cinematographic equivalent of a Jimmy Buffet song (to the point that the famously laidback songer-songwriter appears as himself).