A Brief History of The Cave Diving Line Arrow – The Forrest Wilson Story

Here at ProTec Dive Centers we are passionate about cave diving! And, we are massive geeks about cave diving history and technology. Recently, I sat in on Cristian Toro’s lesson on cave diving navigation. We got to talking about the history of cave markers and the origin of line arrows. Following our discussion, Patrick Widmann, Resident Cave Explorer and Director of Training, contacted Forrest Wilson (the inventor of the line arrow as we know it), to learn the story of the arrow’s development. The following is summary of the personal correspondence between Patrick Widmann and Forrest Wilson.

Cave Diver Installing Line Arrow - Credit Global Dive Guide

Finding The Way Out With Arrows

The use of arrows to indicate the direction of the the exit originated in dry caving. Early cavers used smoke from torches or carbide lights to leave smoke arrows on the cave walls.

The Evolution From Dry Caving to Cave Diving

When the cave diving pioneers started cave diving in Florida, nobody left permanent lines in underwater caves, therefore there was no need for markers. The divers just reeled in the line as they left the cave. According to Wilson, John Harper was the first to leave line in caves, but he didn’t think of line markers. Other cave divers used things like clothespins, or the outrigger clips used by fishermen, especially once T’s and complex navigation became popular. Following a cave diving accident in Florida most of the T’s were with gaps, requiring jump reels.

In 1976, the death of a lost cave diver at Peacock Springs in Florida prompted the development of a marking system. Lewis Holzendorf invented the idea of using triangles made of duct tape folded on the line as “arrows” thus they were known as ‘dorf’ markers. Dorf markers suffered two major flaws: they folded up or deteriorated over time. However, it is possible to find the remains of scrappy ‘Dorf’ arrows on the lines in caves such as Xunan Ha, a cave re-explored and mapped by Hans Kaspersetz and others.

Innovation and Durability of Cave Diving Line Arrows

At an early National Speleological Society-Cave Diving Section Workshop, Sheck Exley asked Wilson to lead a discussion. The workshop was on the development of durable line arrows. Wilson’s idea was to use a thin plastic triangle that could be folded on the line, and snapped closed, much like a Dorf marker. One of Exley’s requirements was to keep the name of the marker the Dorf marker, since Lewis was a good friend of his. Original Cave Diving Line Arrow Illustration from NSS-CDS WorkshopDuring the workshop Roger Werner drew a triangle on the blackboard with slots, but they had no holes or notches and would never stay on the line.

Wilson tried several things, including three slots, ending in holes. They stayed on a line fairly well, but took too much time to install. Next he tried two slots with holes centered on the slots, but they didn’t stay on the line very well. Accidentally, Wilson drilled the holes offset from the slots, and those did stay on the line.

Photo of an original cave diving line arrow prototype with 3 slots and offset drilling

I’ll Never Be Able to Sell Another Line Arrow!

Forrest Wilson hand made 100 arrows and took them to the Branford, FL dive center to be sold. When Wilson brought a second batch of line arrows to the shop, the shop owner told Wilson they would never be able to sell the arrows. The shop owner said,

“There are only 10 caves, and if you put 10 arrows in each cave that would be 100 arrows, and he wouldn’t ever be able to sell another line arrow.”

All of the hand made arrows Wilson created were sold. One of Wilson’s students owned a cave rope manufacturing company.  He requested 1 “perfect” arrow to use for an injection mold. Eventually, Dive Rite bought the mold from him. The rest, as they say, is history.

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