Line protocols in cave diving
One of the main reasons for cave diving fatalities involves the lack of a continuous guideline. Guidelines are the lifelines 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 ambient air. It can be either for not running a temporary line from the open water to the permanent guideline or passing from one line to another.
For maximum safety, cave divers follow a continuous 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 ensure a properly installed guideline for further exploration and visiting cave divers.
The permanent lines are often referred to as the mainline. They can begin close to the cave exit or further into the cave hidden from open water divers and prevent them from going into the cave without proper training. Divers travel to the mainline with a primary reel to keep a continuous guideline from the open water.
Navigation in Caves
There is more than one permanent line in most caves, especially in the Yucatan peninsula in Mexico. Therefore, the divers have to navigate inside the cave. There are permanent intersections, referred to as a “T. “
Sometimes a diver has to move from one line to another physically; 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 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.
Laying line in a cave
Proper use of reels and placement of lines is essential for efficient cave diving. The line has to be laid, maintaining tension. The diver should place it close to the cave floor so divers can swim above it.
A primary tie-off should be made in open water where a direct ascent to the surface is possible. A secondary tie-off follows it 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 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). Personal non-directional markers are mark locations or exits and will not confuse 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.