Four words: "Nautron respoc lorni virch." What's it mean? We don't know… and that's the point. The crew of the Nautilus is a total mystery.
They speak an unidentifiable language. Aronnax, Ned, and Conseil can't even figure out how many of them are on board. Like Nemo, they do nothing to reveal their nationalities. Well, almost nothing.
Just once, in the horrible battle against the squid, when an unlucky sailor is snatched up, he screams out for help in French. Aronnax knows, then, that these men are, well, men—he feels a sort of fellowship with this countryman he barely knows.
This little slip-up gives us a bit more evidence that Nemo and his crew are really human beings. While they're sort of mythic and mysterious, they're also regular people who are just trying to live their lives, forget the past, and start anew.