In the early years of cave diving, it was thought that cave lines leading to the exit should be thicker, less prone to stretch, and abrasion resistant. Gold kernmantle was chosen because of this. The Gold gives a visual clue, while the thicker line gives a tactile clue if in a lights out situation. Also, in times of stress divers tend to put a lot of tension on the line, so the much sturdier line will not break or chafe as easily.
