User blog comment:UltimateTORINOR/A Simple Question.../@comment-1874924-20100625143603

I went back and reread that scene. Arbok himself never mentions drowning, although Jason does.

How about this: Jason was anthropomorphizing Arbok; the other campers (who presumably have no experience with talking objects) made certain assumptions about Arbok, precisely because he can talk; and Arbok himself, while in no physical danger, knew that he doesn't float and didn't relish the prospect of being entombed in lake mud for a couple of geologic periods.