Line protocols in cave diving
Guidelines are the life lines used by cave divers to reference the exit in underwater caves. In case of loss of visibility the guideline will lead to the way out of the cave, back to the surface and to ambient air. One of the main reason for fatalities in cave diving involves the lack of use of a continuous guideline. It can be either for not running a temporary line from the open water to the permanent guideline or for passing from one line to another.
For maximum safety, cave divers follow a continous guideline that can lead them all the way to the surface, even in total darkness. Directional markers such as arrows and personal non-directional markers such as “cookies” or REMs on the lines clearly indicate the exit.
Permanent lines are installed permanently in the cave to insure a properly installed guideline for further going exploration and visiting cave divers.
The permanent lines are often referred to as main line. They can begin close to the cave exit or further into the cave hidden from open water divers and prevent them to go into the cave without proper training. Divers travel to the mainline with a primary reel in order to keep a continuous guideline from the open water.
Navigation in Caves
In most caves, especially in the Yucatan peninsula in Mexico, there are more than one permanent line therefore the divers have to navigate inside the cave. There are permanent intersections, referred to as a “T“.
Sometimes a diver has to phisically move from one line to another this is a jump. It can go from the end of one line to the middle of another, or from the middle of a line to the end or middle of another.
A gap is when going from the end of one line to the end of another.
Personal line markers properly mark the exit. It has to be in a clear way in order to be understood in zero visibility. The diver will be able to find the way to the open water area of the cave entrance.
Gap and/or Jump Lines
Divers have to install a temporary gap or jump line to go from one line to the other. Line markers such as directional or non-directional should also indicate and mark the exit.
Proper use of reels and placement of lines is essential for efficient cave diving. The line has to be laid maintaining tension. It should be placed close to the cave floor so divers can swim above it.
A primary tie off should be made in open water where direct ascent to the surface is possible. It is followed by a secondary tie off in the cavern zone. Should the primary tie off come loose the second one will keep the line in place. Further on a tie-off or placement must be made whenever changing direction in order to avoid line traps.
Line markers indicate directions or mark survey or science stations. They can be directional (arrows) or non-directional markers (cookies, clothespins, REM). Personnal non-directional markers are mark locations or exits and will not cause confusion for other teams.
You will learn more about the use of guidelines and line markers and practice their uses in real caves and various scenarios during your cave diving training.