Charles Ellicott Commentary Job 38:16

"Hast thou entered into the springs of the sea? Or hast thou walked in the recesses of the deep?" — Job 38:16 (ASV)

The search of the depth — that is, the secret recesses of it. The “springs of the sea” are rather, perhaps, the mazes, intricacies, etc. of the trackless, pathless deep. This leads to the cognate thought of the bottomless pit of death (Job 38:17).