“Blue Crush” knows something most surfing movies don’t acknowledge–that many non-pro surfers endure blue-collar jobs as a way to support their surfing, which is the only time they feel really alive. Surfers in the movies have traditionally been golden boys and girls who ride the waves to Beach Boys songs–and live, apparently, on air. In “Blue Crush,” we meet three Hawaiian surfers who work as hotel maids, live in a grotty rental, and are raising the kid sister of one of them. Despite this near-poverty, they look great; there is nothing like a tan and a bikini to overcome class distinctions.

The movie, based on Susan Orlean’s magazine article “Surf Girls of Maui,” resembles the Nik Cohn journalism that inspired “Saturday Night Fever.” Both stories are about working-class kids escaping into the freedom and glamor of their obsessions. We hear fascination in their voices when they stop at a gas station and see, at another pump, famous professional women surfers who are in Hawaii for a big tournament. While it is true that Anne Marie might be able to make money as a member of a pro surfing team, it is also true, as it was of Tony Manero in “Saturday Night Fever,” that other things distract her, especially romance. She is not single-mindedly focused on her career.

And then of course the movie ends with the big showdown, with waves of awesome strength and feats of great surfing, with all the necessary dangers and setbacks. Even here, it doesn’t settle for what we thought was the predictable outcome.