Jamieson, Fausset and Brown on Job 6:18

18. turned aside--rather, "caravans" (Hebrew, "travellers") turn aside from their way, by circuitous routes, to obtain water. They had seen the brook in spring full of water: and now in the summer heat, on their weary journey, they turn off their road by a devious route to reach the living waters, which they remembered with such pleasure. But, when "they go," it is "into a desert" [Noyes and Umbreit]. Not as English Version, "They go to nothing," which would be a tame repetition of the drying up of the waters in Job 6:17; instead of waters, they find an "empty wilderness"; and, not having strength to regain their road, bitterly disappointed, they "perish." The terse brevity is most expressive.