Naufrageurs translates to "wreckers" or "shipwreckers". It's a striking and somewhat archaic word that immediately evokes a sense of drama and danger.
In the song, Gainsbourg uses it to describe the naive indigenous people who, in their cargo cult rituals, hope for planes to crash. He then draws a parallel between their desperate hopes and his own desire for an "air disaster" to bring back his lost love, Melody. This word perfectly encapsulates the song's dark, poetic, and almost surreal atmosphere.
Gainsbourg builds "Cargo Culte" — the closing track of Histoire de Melody Nelson — around a real Melanesian religious movement: islanders who watched Allied planes land supplies during the Second World War and later built runways of their own, praying for the cargo to return. He opens almost as reportage: "Je sais moi, des sorciers qui invoquent les jets / Dans la jungle de Nouvelle-Guinée" [I know, wizards who invoke the jets / In the jungle of New Guinea], describing islanders scanning the sky for planes that might still carry treasure.
Halfway through, the song turns from anthropology to heartbreak: he starts calling for Melody Nelson herself — "Où es-tu Melody / Et ton corps disloqué" [Where are you Melody / And your dislocated body] — praying for a plane crash to bring her back, the same way the islanders pray for cargo. By the end he is reduced to repeating her name alone over Jean-Claude Vannier's orchestral swell, the two searches — for aircraft, for a lost lover — collapsing into the same doomed waiting.