Document Objective: To promote consistency and serve as a guide in the installation of system lines by the Filipino Cave Divers.


As part of a series of articles, this segment outlines the preferred method for the installation of permanent system lines in the underwater cave systems in and around the Philippines. Through its membership and participation in the National Cave Committee, Filipino Cave Divers is tasked with creating safety protocols, supplementary classification and protection of the underwater cave systems.

Definition of terms relative to Permanent Lines:

System Navigation refers to the use of a line and the appropriate line markers in a cave system to aid in referencing one’s position and planning and following a route.

Permanent/Main/System lines refer to guidelines that are installed by an agency to facilitate a full experience of the exploration of a cave system for visiting cave divers. This is differing from an exploration line which is typically installed on the fly by a team when the objective of the dive is to understand an unknown/unexplored cave’s general characteristics. Permanent lines are meant to be a secondary tool to reference the exit of a cave system and are not to be removed or altered by unauthorized divers.

Cave Side – directional reference to the inner parts of the cave.

Exit Side – directional reference to the exit of the cave or non-overhead environment.

System Markers – directional or non-directional markers that are installed on the line as part of the Permanent Line. They may be directional in that they reference the closest physical exit at a given point or non-directional in that they may give information such as points of interest or distance from exit, etc. System Markers are treated as permanent and should never be removed unless authorized.

Line Arrows – point to nearest physical exit. NOTE: not to be confused with “personal or team exits.”

Cookies – may be used to mark points of interest in a system line. Points of interest should be specified in the Underwater Cave Map for the Site. Cookies should be labelled by letter or by number and may or may not include details.

Referencing Exit Markers – are generally, not used in permanent lines as it can confuse visiting divers.
T – refers to a split on the line creating two possible directions of travel. May or may not be installed with a cookie. It is discouraged to use a Line Arrow or an R.E.M. as these are typically reserved for temporary jumps.

Trifurcates – Refers to a split on the line creating three or more possible directions of travel.Fig.1

Jump – is an area in the system line where a side-passage or another line may be explored or connected to. It is indicated by two arrows separated by a few inches that also reference the closest physical exit (known and verified to be a faster/shallower/less restricted).

Gap – is a potential connection between two lines that have no change in direction. It’s a break in the line.


Midpoint – indicated by two opposing arrows if there are two ways or more to reach the exit of a cave.

Circuit – is a line that returns to the exit using a path different from your inbound.

Line Ties – a line-on-line connection after a wrap, drop tie, or tie off.

Goal of a Permanent Line:

The purpose of a Permanent/System/Main (sometimes also called a traverse) Line is to provide a permanent navigational tool that will reduce the task load on cave divers, ensure that a cave system is kept clean from excessive lines, to reduce diver impact on the cave and to provide a safe way out if necessary.

System Lines should be periodically inspected and maintained. Any breaks or slack on the line should be promptly reported to and repaired by the Cave Custodian (see below).

Main lines or System Lines are laid in accordance to the following principles:

  • It must begin close to the cavern zone or exit of the cave but inside enough to dissuade open water divers from venturing into the cave.
  • It must facilitate a safe and efficient way to exit minimizing line crossing and leaning towards giving priority access and ease to an exiting team in the case of an emergency.
  • It must be environmentally appropriate in a way that the line considers the specific characteristics of the cave. For example, if a cave is a no flow silty bottom, the line should be laid along a reasonable height to ensure its visibility. Its height will also encourage divers not to be too close to the floor of the cave, thus avoiding silt outs as well.
  • Line ties/knots/chokes should be facing the “open side” (larger side) of the passage.
  • Line ties on system lines should have a double wrap before the choke.
  • Sufficient line markers/arrows (large size) should be placed in the system line to aid no-viz exits. Even more line arrows in areas prone to silt outs.
  • Arrows must always point towards the nearest physical exit.
  • Must be free from line traps.
  • If more than one path to exit is observed, two opposing arrows close together must be placed in the exact midpoint of the system line.
  • KISS. Too many ties are distracting and inefficient so we keep it simple. Ties are placed on direction changes, distance, depth changes and angles. The driving factor is to preserve the integrity of the line by minimizing friction against the environment and providing less verification points for exiting no-viz divers.


Secondary Objectives:

Generally, a line is preferred on one side, right or left would depend on the cave’s orientation and characteristics. Line changes (changing from left to right with the corresponding line ties) should be kept at a minimum to primarily facilitate ease of emergency exits and for elegance.

The rule of thumb for height is that it should allow a diver to stay in the middle of the chamber to neither create silt nor hit the roof. It is highly discouraged to put the line in a spot that would force the diver to be below it (for reasons of line visibility, accessibility and as an entanglement hazard). In general, therefore, any place from below the diver to beside but slightly below is fair game. In the instances where no option is available, placement should ensure no threat of entanglement and line traps.

The quality of a good line, other than the material used for longevity purposes, is the amount of tension on the line. A well laid line will have the minimum number of wraps to hold it in place, following the principle that the more wraps are put on the line, the more prone it is to breakage. Line tension should be firm, knowing that slack kills, and enough to allow the placement of both system markers and temporary (team/visitor) markers as well. It is preferred to have a white line with a thickness of 3mm on the main system line and 1mm on side passages to enable tactile identification in no-viz.

Permanent ties and tie-offs are to be attached to non-fragile structures of the cave. Under no circumstances is the introduction of a foreign object permitted in any cave for purposes of creating a permanent system line. Keep the cave as natural as possible.

Cave Custodians:

A cave custodian is the primary point person who protects and maintains the integrity of the underwater cave. This is not limited to an individual and can be any legal entity (lgu, association, corporation, etc.) that has capacity to perform the maintenance of the caves. Each cave custodian has the following duties, either directly or in-directly:

  • Maintain an activity log (tourism, scientific study, survey, etc).
  • Oversees the maintenance of system lines and repairs when necessary.
  • Possesses a survey map of the underwater cave system.
  • Setup a localized Emergency Action Plan that can mobilize the right people if an emergency arises.

End of Article.

Note: The Filipino Cave Divers, as an active National Cave Committee member is coordinating with respective Regional Cave Committees to update and extend underwater support to the capacity of the Cave Focal Persons as defined by BMB Technical Bulletin No. 2017-01.

Article by:

Juan Naval
Juan Naval

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