It sounds like your going under a porch or house on blocks.
I'd suggest taping a flashlight to it as a headlamp, and mount a can of bug spray on the housing for the spiders. Then tie a rope to your leg so someone can pull you back out.
That one empty pockets put up is a nice mod but i do not think he made that he just got a picture off the net….… but you could get a VIBRATECTOR it has a 4 inch head and detects 6 inches deep and it is water proof a lot of divers use them they are a nice pin pointer..