by Andy Davis

Disclaimer:   These notes accompany a professionally supervised advanced wreck diving workshop, aimed at developing specialist skills for qualified wreck divers.  This information is not a substitute for gaining proper experience under qualified direction.  Wreck penetration is a very hazardous scuba diving activity.  Divers should not attempt the techniques detailed in this article without appropriate support or supervision.  Training drills should always be mastered in an open-water environment, before they can be applied, or relied upon, within an overhead environment.

What is Advanced Wreck Diving?

USS New York Subic Bay Engine Room EntranceAdvanced Wreck Diving is the continuation of wreck diving education beyond the basic/introductory training provided by mainstream diving agency ‘wreck diver’ courses.  It specifically focuses upon the conduct of wreck penetration, providing skills, drills and protocols necessary to mitigate the substantial extra risks posed when diving within man-made overhead environments.

Recreational Wreck Diving Limits

Recreational wreck divers should observe the following limits to penetration of wrecks:

  • One continuous guideline
  • No restrictions*
  • No decompression
  • 30m max depth
  • No complex dives, including jump lines, gap lines or permanent lines
  • Rule of thirds air management on single/double tanks
  • Max distance to surface (horizontal plus vertical) is 40m/120ft
  • Within the ‘light zone’, where natural light penetrates and illuminates
  • Ability to clearly see the exit at all times
  • No severe risk of silt out

*A restriction is defined as a space too small for 2 divers to pass through simultaneously whilst sharing air.

Advanced Wreck Diving – Required Skills

Recreational wreck divers should possess the following competencies before penetrating wrecks:

  • Wreck Diving Subic Bay USS New York

    Wreck divers need well tuned buddy skills to ensure safety when venturing into shipwreck environments

    Buoyancy Control. Ability to maintain +/- 50cm of target depth, whilst otherwise task loaded

  • Trim.  Ability to maintain flat horizontal trim, with slightly head-down positioning.
  • Propulsion. Ability to utilize non-silting fin techniques, including frog kick and modified flutter kick.
  • Control. Ability to demonstrate positioning control without reliance on hands. Efficient use of helicopter turns and back kicks for maneuverability within confined spaces.
  • Streamlining. Divers’ equipment demonstrates effective streamlining, efficiency and adequate redundancy, with no obvious entanglement hazards and minimum failure points.
  • Gas Management Ability to accurately plan and manage gas requirements for the planned dive, including contingency reserves.
  • Dive Planning. Ability to precisely plan a no-decompression dive, conduct effective risk assessment and confirm effective contingency/emergency plans prior to water entry.
  • Navigation. Ability to effectively navigate back to the start point, using compass and natural navigation techniques.
  • Buddy/Team Skills. Ability to plan dives and follow those plans in a coordinated way with a diving buddy/team, including the ability to conduct effective emergency drills.  Buddy diving.
  • Situational Awareness. Ability to maintain awareness of depth, time, no-decompression limit, surroundings, navigational location and buddy/team, whilst otherwise task loaded with specific skills.

Advanced Wreck Diving – Specialized Equipment

El Capitan Wreck Subic Bay PADI Course

Proper wreck diving equipment helps to mitigate the additional risks inherent in that environment

In addition to standard scuba diving equipment, the following specialized equipment should be carried for advanced wreck diving penetration:

  • Penetration Reel. A primary reel with sufficient line to penetrate a planned distance into the wreck.
  • Emergency/Safety Reel. A contingency reel for conducting emergency procedures (detailed later).
  • Primary Torch. A bright, high-power torch capable of providing sufficient illumination and signaling capacity within no-light zones.
  • Back-Up Torch. A small-size torch capable of one-handed operation, with long capacity battery life.

Advanced Wreck Diving – Dangers

The primary danger within a wreck is becoming lost and unable to exit.  When gas supplies are finite, becoming lost within a wreck is a life threatening situation.  Divers drown inside ships wrecks every year.

Advanced Wreck Diving

Restriction, silting and darkness are considerable hazards when penetrating wrecks.

  • Orientation. Ship wrecks are rarely orientated in a normal vertical position.  Sloping passageways, ‘upside-down’ rooms, miss-orientated stairwells and other features can all lead to the diver become rapidly disorientated.  Determining an exit route from a wreck is rarely obvious or instinctive.
  • Silt. Most ship wrecks contain a large amount of silt.  Silt can be defined as congregation of fine particles formed from organic or inorganic matter.  Mud and sand can be swept along in a current and then settle and deposit within a wreck, covering the wrecks floor areas and adhering to walls, fixtures and fittings.  Organic matters and other objects (wood and materials used in the ships construction) can decompose and form sediment. Metal will rust and disintegrate into fine particles.  If the diver disturbs silt (or even creates water movement which then disturbs silt), then it will rapidly rise into the water and lower visibility. Wreck divers must perfect non-silting fin and control techniques to reduce occurrence of disturbing silt.  Even a very cautious diver will unavoidably disturb silt, as their rising bubbles can dislodge silt on the ceiling.   Disturbed silt within a confined space can rapidly deteriorate visibility to zero.  Do not underestimate how ‘zero’ that is!
  • Collapse. Wrecks rust and decompose over time.  Divers can disturb heavy object that can then injure them or block exit from the wreck.  Never exert force on objects within a wreck, no matter how secure or solid they may seem.  If the diver is passing through an open-door, they should ensure that the door cannot swing shut behind them.  If unsure, use some line to tie the door into an open position.
  • Current.  Current can flow in an unpredictable manner around, and through, a ship wreck.  This flow of water may also vary in strength during the course of a dive.  Water flow may oppose exit from a ship wreck, or could drag a diver into the wreck, or areas of a wreck, they they do not wish to enter.


Advanced Wreck Diving – Air Supply

When operating within an over-head environment, the diver should pre-plan their gas requirements to ensure that sufficient volume is carried.  They should also pre-plan precise reserve/contingency levels based on air-sharing with a buddy.  See ‘Gas Management‘.

Gas planning should also determine a ‘turn-point’ of pressure that follows the principle of ‘Rule of Thirds’. This is taught to all wreck students – however, that principle needs to be applied on the basis of air-sharing.  That means some understanding of air consumption rates has to exist, in order for a safe turn-point to be decided that protects sufficient gas for both divers to exit.

Gas Redundancy

Whilst not mandatory, recreational wreck divers should seriously consider the use of redundant air sources.  Redundant Air Source Article.   These could include:

Pony Cylinders

Scuba Diving Redundant Gas

A ‘Pony’ cylinder can be used to provide a redundant air source. The required capacity of the cylinder should be calculated for the planned dive.

An emergency cylinder with separate regulator that supplies sufficient air for both divers (diver + buddy) to reach the surface from the deepest limit of their penetration.  Rock Bottom Gas Management principles should be used to determine the required volume to cover this contingency.

Independent Double / Sidemount Cylinders.

Two cylinders of equal size, which combined contain sufficient gas for the planned dive.  Rock Bottom Gas Management principles should be used to determine the required volume to cover an air sharing emergency using a single cylinder.  Minimum reserve for air sharing ascent should be based on a worst-case scenario that one cylinder is unavailable.  Gas volumes from both cylinders should be matched as the dive progresses (i.e. the diver utilizes 20BAR from one cylinder before switching to the other cylinder and using 20BAR, then switching back for 20 BAR etc etc)

Isolated Manifold Double Cylinders.

Wreck Diving Double Cylinders

Independant or manifolded double cylinders offer an excellent solution for providing redundant gas

Two cylinders of equal size, joined with an isolator manifold, which combined contain sufficient gas for the planned dive.  Rock Bottom Gas Management principles should be used to determine the required volume to cover an air sharing emergency using a single cylinder.  Minimum reserve for air sharing ascent should be based on a worst-case scenario that has necessitated the closure of the manifold and shut-down of one cylinder.

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Note:Small capacity ‘Spare Air’ type ascent cylinders are unlikely to contain sufficient air for a protracted exit from a wreck plus ascent to surface.  Neither do they permit effective air-sharing between two divers.  Therefore, these types of cylinders are not recommended for wreck penetration diving.

Gas Mixture

If appropriately trained in their use, divers should consider the optimum gas mixture to conduct the dive.  Use of nitrox can be significantly beneficial on wrecks; where the dives are typically square profile.  For deeper dives, the risk of inert gas (nitrogen) narcosis presents excessive risks when conducting wreck penetrations.  The use of helium within the breathing mixture is an effective way to minimize the impact of narcosis.  Recreational (normoxic) trimix courses are becoming increasingly more popular and present a good solution for recreational wreck penetration below 30m/100ft.

Rule of Thirds

wreck diving course subic bay

Know your Gas Plan before entering a wreck

When entering into overhead environments, divers must maintain gas reserves based upon the Rule of Thirds.  This rule dictates:

1/3rd of Gas for entry (up to the turn-point).

1/3rd of Gas for exit and ascent.

1/3rd of Gas for reserve.

The gas turn-point for a team/pair is dictated by the diver who reaches their 1/3rd first (note: deco/no-deco bottom limits may determine a turn-point before this).

Advanced Wreck Diving – Reels & Lines

The following types of reels may be used for different purposes when wreck diving:

Permanent Reel.

A permanent heavy duty, line that is laid within the wreck.  Typically this will contain 1” or thicker nylon-based line.  Permanent lines are often laid on regularly frequented wrecks.  The lines are commonly started several meters within the wreck, to prevent temptation for un-trained and/or insufficiently equipped diver to enter the wreck.

Primary Guideline.

This is the main penetration reel used by wreck divers when penetrating wrecks. Typical line length will be in excess of 50-100m.  Line should be 24-36 gauge braided nylon. The reel may be a plastic or metal winding reel (ratchet or tension controlled), or it may be a large capacity finger spool.

Jump / Gap Spool.

This is a small capacity (20-30m) reel that may be used to create a ‘line bridge’ between two other lines.  For instance, when a permanent line starts within a wreck, or where two permanent lines within a wreck are separated. Finger spools are typically used for this purpose.

Safety Spool.

This is always a finger spool, of at least 150’ length that is carried only for emergency/contingency circumstances.

Exploration Reel.

Primarily used for cave, not wreck, exploration. An exploration reel is a very high capacity reel that will contain in excess of 2000’ of braided nylon line.

Other factors to consider with reel & line selection:

  • Line Color. White is the most reflective color and therefore a popular/prudent choice for primary/penetration lines.  It is wise to choose a different line color for the safety spool, to prevent confusion when contingency procedures are used.
  • Distance Knots.  If you desire to monitor distances when penetrating wrecks, tie small knots into your penetration line at equal intervals.  This is useful for mapping wrecks and can also be used to implement a linear ‘turn-point’ at pre-designated maximum penetration distance.
  • Clips.  Do not use any form of swing-gate clip in conjunction with a reel (ideally, don’t use these at all).  These clips (i.e. carabineers) do not require any diver input in order to catch and secure line.  Any accidental contact can lead to the clip entangling line.  Only use clips that require direct and deliberate user input/control.  Bolt snaps are ideal.

Advanced Wreck Diving – General Team / Buddy Procedures

An ideal team size for wreck penetration is 2-3 divers.  More than this amount can lead to an increased risk of silting, plus potential confusion that can lead to a lost diver.  With 3 divers, the 2nd diver will be responsible as a ‘link’ that ensures contact with the 1st and 2nd divers; confirming that the whole team is present.   If there were 4 divers, then it would be impossible for a single ‘link’ diver to confirm that the entire team was present in low visibility.

Team Roles and Responsibilities

As part of the pre-dive preparation, it is important to assign team ‘roles’.   These will include:

  • Reel Diver. The diver who uses the primary reel to lay line on entry and retrieve the line on exit.  They have primary responsibility for navigation. The reel diver is first-in and last-out.
  • Link Diver. (in team of 3) The diver who maintains team cohesion by ensuring that the reel diver and the support diver are on either side of them at all times.  They pass communication between the other two divers.  They are always number 2 in the order.
  • Support Diver. The diver who maintains primary responsibility for adherence to the dive plan.  They will be the last diver in order.  Their primary role is to maintain overall situational awareness, including monitoring depth, time, gas supply and no-decompression limits.  They should ensure that turn-points (gas or linear) are adhered to. Upon exit, they would lead the team through the required ascent and stops.

The second diver in order will also be responsible for supporting the reel diver during line laying and retrieval.  This task includes the maintenance of tension on the line, checking and scrutinizing knots/tie-offs (inwards).  They will also help provide greater illumination for the reel diver.

Team Positioning

Teams of divers can position in different ways, depending on the wreck environment.  These are the main options:

  • Single File. Single file travel prevents disorder and helps to maintain team cohesion and awareness.  It is also preferable in more confined spaces

Single File on a guideline for wreck penetration

  • Staggered. Staggering  the team on either side of the guideline provides more forward awareness for each individual diver.  This helps ensure that divers can look ahead, orientate themselves and anticipate their travel.  It also helps prevent disorientation during exit.

Staggered file on a guideline for wreck penetration

Advanced Wreck Diving – Communication

Wreck penetration divers should be prepared to maintain contact with the guideline at all times. This means that one-handed communication signals are required, especially one-handed communication of numbers.

Hand Signals

Wreck diving requires certain specific signals. These hand signals need to be performed with only one hand, as the diver should retain a free hand for controlling the reel, operating their light and/or maintaining contact with guideline.  Specific advanced wreck diving signals will include; ‘Tie-Off’ and ‘Turn-Point’.

  • Numbers. Use a single hand to communicate numbers, using the following signs:
Wreck diving hand signals

Wreck diving hand signals

Light Signals

Light signals are very important during wreck penetration.  There should be both active and passive communication.

  • Active Communication.

These are deliberate signals given with the light.  A circular ‘OK’ signal should be exchanged at regular intervals.  This should be given within the divers field-of-vision to prevent the need for constant turning. To indicate a problem and/or gain other divers immediate attention a back-and-forth motion should be used with the torch inside the leading divers field-of-vision.

  • Passive Communication.

These are the use of lights to maintain constant situational awareness and cohesion of the team.  It is important for wreck divers to regularly (every 15-20 seconds) sweep their beams across the field-of-vision of divers forward of them.

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Advanced Wreck Diving – Guideline Procedures

Following a Guideline

  • Distance from Line The diver should never be more than a short arms reach from the line.  In the event of sudden visibility loss, or other emergency, the diver should be able to instantly reach and hook their arm around the guideline.
  • Equipment. The diver should not have any dangling or loose equipment that could become entangled with the line.
  • Trim. The diver should maintain horizontal trim to prevent unnecessary contact against the line, with the risk of entanglement.
  • Positioning. The diver should be at the same level, or slightly higher than, the guideline.  If the diver is below the guideline, then the risk of entanglement increases.  Entanglements that occur behind the diver are much more difficult to resolve.
  • Entanglement. Getting entangle in the guideline can become a very serious safety hazard.  The effort to disentangle can cause line breakage and/or cause silt to be disturbed in that area.  Be calm and methodical when dealing with entanglements.  Do not cut the guideline until contingency procedures have been made (see line cutting drill below).  If the entanglement is in a position that you cannot easily reach, signal your buddy and allow them to assist.
  • Be aware of other lines Divers should be aware that other lines may be laid within a wreck.  Note the color and type of your line, positioning markers, tie-offs etc to prevent confusion.  Use distinctive and/or personally modified line markers. Being side-tracked onto a different line can lead to team separation and being lost within the wreck.
  • Compass. Use a compass to give an overall orientation and direction of travel.  This can be extremely useful if a diver losses the line.  Be aware that wrecks can interfere with the magnetic alignment of a compass.
  • Speed.  Penetration entry of a wreck should be deliberately slow and careful.  If the entry into a wreck is maintained at a forced slow pace, then it provides a reassurance that the exit can be achieved quicker than the entry.  This enables a consequently slower pace of exit and provides some extra measure of conservatism in respect of gas management/turn-points.  Divers should remember that an
  • Exit.  Divers should remain aware that any margins for error are greater on exit from the wreck.  Time and gas restraints are more critical and visibility is often reduced.  Any exit in low visibility, or other emergency, will be particularly stressful and air consumption will be elevated.
  • Additional Tasks. Where the dive team intend to accomplish additional tasks inside the wreck (survey, inspections, artifact recovery, photography etc) these must only be undertaken on the entry portion of the penetration.  Once the turn-point is reached and divers begin to exit the wreck, total focus must be maintained on a direct and timely exit into open water.
  • Back Referencing. During entry into a wreck, make a habit of frequently looking behind and familiarizing yourself with the exit route. This will make the exit travel easier, especially if there is a lost or broken line.
  • Line Contact. In low/zero visibility, the diver should maintain a constant and secure contact with the guideline.  In doing so, they should not exert any significant force onto the line – which may be pulled against sharp metal inside the wreck and severed.  Never pull on the line.
  • Holding the Line. Do not grip the line tightly in your hand.  Hold the line within a loose circle formed by your thumb and forefinger.  To prevent the line being pulled between those fingers, use the next finger to ‘lock off’ that circle.
wreck diving skills

Air pockets inside wrecks may not be breathable. Keep your regulator in place

Laying a Guideline

Guidelines are essential within any wreck penetration where loss of visibility can occur.   In very low, or zero, visibility the guideline

Wreck diving guideline

Line-laying for wreck penetration requires a lot of practice. Aim to ingrain the skill so that it doesn’t present excessive task loading

represents the divers only certain exit of the wreck. Consequently, a guideline should be treated as a ‘life or death’ aspect of the dive.

  • Visibility. When laying a guideline, the diver should always assume a worst case scenario that they will be exiting the wreck using the guideline in zero visibility. This mindset ensures that the line will be laid effectively to ensure a swift and uncomplicated exit.
  • Line Start. The line must be started in open-water outside of the wreck.  It should have a primary and secondary ‘tie off’ outside of the wreck for security.
  • Line Traps. Line traps are areas where the line can be laid, which divers cannot pass through.  Be aware of potential line traps when laying a guideline.  Also be aware that a loose line can float into areas that will form line traps.
  • Stations. A ‘station’ is any point where the line comes into contact with the environment. This is typically where a change in depth or direction occur. Such contact should be either a placement or a tie-off.
  • Placement. Placement is a station where the line rests passively against an object.  When a placement is necessary, or unavoidable, the diver laying line should ensure that the line it not loose and liable to drift into a line trap.
  • Tie-Off. A tie-off is where the line is actively attached to an object.  This provides security and helps maintain constant tension along the line.
  • Wrap Lock. The wrap lock is a method of forming a tie-off along the line to an object.  It is achieved by wrapping the line 1 or 2 times around the object (front-to-back) and then locking it by looping the reel over the line and pulling it tight.  Wrap locks should be created to ensure that a continuous line is maintained.
  • Frequency of Stations. The diver should attempt to minimize the frequency of stations, where possible. Stations are time consuming to create and retrieve. However, a station should be created at any change in direction and depth.
  • Line Location The line can be located in various positions during a penetration.  These are the primary options:
    • Along the Floor.  This is easy to follow (reaching down from above) and offers the least risk of entanglement.  However, it offers the greatest risk of silt disturbance.
    • Along the Wall.  Can cause the divers to contact/bump the wall, get entangled with fixtures and the line can only be followed with one hand. This necessitates using a different hand to follow the line in each direction.
    • Mid-Water. The line can be tied between fixed points, transiting through water away from any obstructions, floor, ceiling or walls.  This offers many options for movement and is easy to follow.
    • Along the Ceiling. This is the most dangerous option. It is hard to monitor the line and easiest to lose sight of it.  There is more chance of line entanglement behind the diver and there exists the chance to accidentally roll the cylinder valve closed if contact is made against the ceiling.
  • Line Marking.  It is a wise precaution to mark the line regularly to indicate the direct of exit.  Directional arrows, clothes pegs or other markings can be placed on the exit side of stations to ensure orientation.  Ensure that line markers are personally modified, to prevent confusion between teams.  Ideally, this should be ‘tactile’ – so you can feel the identification in zero viz.  This will prove particularly important if the diver lost and then found the line, but became confused about the direction of exit along the line.  If a jump/gap line is used from the primary guideline, then markers should be left on the exit side of the line joint.  Never interfere with line markings on your, or other, lines.

Wreck guideline marking a jump lineMarking a tie-off for exit on a guideline when wreck diving

Advanced Wreck Diving – Dealing with Silt

Divers can easily disturb silt within a ship wreck.  Inside of confined spaces, disturbed silt can be very concentrated in the water which reduces visibility to zero.  Heavy silting will prevent even strong torches from penetrating even a few centimeters.  Disturbed silt can persist within a confined space for hours or days.

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What Causes Silt-Outs?

Silt can be disturbed due to the following causes:

  • Accidental contact. The diver accidentally makes contact with the floor or other object that is covered in silt.
  • Water movement.  The diver disturbs water which consequently raises silt.  This is common if bad fin techniques are used and/or if poor trim (head-up/feet down) causes water thrust from the fins to drive downwards into silt on the wreck floor.
  • Sculling/Grabbing.  Using the hands to maneuver can disturb silt via water movement.  Grabbing onto objects within the wreck can also raise silt.
  • Exhaled Air Bubbles.  This is unavoidable, unless you dive with a closed-circuit rebreather.  Rising air bubbles can displace silt that has accumulated on upper surfaces inside the wreck.

If the diver disturbs silt, which may significantly limit visibility, then the penetration should be immediately aborted and the team should seek direct exit from the wreck.

Dangers of a Silt-Out

Wreck Diver Course Subic Bay

Silt-out inside a ship wreck can make exit impossible. A guideline should be used to ensure your survival

The biggest danger in zero visibility is that one or more divers could lose the guideline and become trapped/lost in inside the wreck.  If the team will become separated from each other it will be impossible to know if team members are safely exiting the wreck, or are trapped/lost inside.

If the team exits the wreck missing a diver, they will have wasted critical time and also lost the ‘last point’ where the team were united – which makes a potential search far greater in scale.

To operate safely in low or zero visibility, it is critical that divers have instinctive-level skills and are not prone to claustrophobia.  As divers may train differently (different procedures, signals etc) for wreck diving, it is important that contingency plans and drills are discussed and agreed upon prior to the dive.

If diving on wrecks with a high potential for silt disturbance, a prudent team of divers may even physically rehearse their contingency drills prior to the dive.

See Video Illustration:  SILT-OUT WRECK DANGER

‘SOAL’ Protocol for Silt-Outs

If a ‘silt out’ occurs, then the whole team should follow this immediate 4-step ‘SOAL’ protocol:


SECURE – Immediately locate and secure yourself on the guideline.  Do not let go until you are out of the wreck.

ORIENTATE – Briefly shade your light (don’t turn it off) and look for light sources that indicate the exit (external light entry) and their buddy (torch).  Sweep the light around the area, to enable other members to orientate with you.

ASSEMBLE – The leading (Reel) diver immediately stops and secures the guideline with a tie-off.  They then remain in position.  The rear diver/s moves forward along the line until they make physical/touch contact with the lead diver.  Each diver will locate and grip the thigh of the next diver.  The team must confirm that all members are present and accounted for.  This is easy for 2 divers.  If there are 3 divers, then the middle diver must confirm that the leading and trailing diver are surrounding them.

LEAVE – Maintaining constant physical contact with the other divers and the guideline, the team must communicate using visual or (in zero viz) tactile signaling.   Tactile signaling comprises the following:

      • Stop                 =        1 squeeze (on the leg)
      • Go                     =        Push forwards (on the leg)
      • Reverse         =       Pull back (on the leg)

Other communication can be achieved by the physical manipulation of the divers hands.  Grab the divers hands and manipulate it to form the signal you wish to communicate. Virtually any hand signals can be given this way in zero visibility.

Constant physical contact with team members and the guideline is not relinquished until all members of the team are clear of the wreck, in open water.

Advanced Wreck Diving – Contingency / Emergency Drills

There are a number of drills that a wreck diver can rehearse for emergencies within a low/zero visibility environments.  Emergency scenarios, especially in low/zero visibility, are extremely stressful.  This can easily result in hyper-ventilation, which can cause CO2 retention (impairment), induce underlying nitrogen narcosis (on deep dives) and drastically increase air consumption.  It is vital to stay calm, maintain steady deep breathing and not put yourself in further risk.  Do not allow any emergency to distract you from maintaining an awareness of your gas supplies and no-decompression limit.  Always ensure you have sufficient gas to reach the surface.

1.      Lost Diver Drill

This drill is used if a diver is missing from the team.  It can be utilized regardless of visibility.  Be sure not to make yourself a casualty – remain aware of your air, NDL and situation.  Never exceed your rock bottom gas.

      1. Maintain contact with the guideline.
      2. Cover your light and observe for your buddies light.
      3. Place a line marker, indicating the exit direction, on the guideline.  This provides a reference of the point where the diver was lost (aiding subsequent search & rescue attempts) and ensures that the searching diver can relocate the exit after performing a search pattern away from the guideline.
      4. Check gas supply, no-decompression limit and calculate/confirm the maximum safe gas reserve that you have for conducting searches and then exiting/surfacing.
      5. Make a firm plan how long you will search for, before exiting to raise alarm/get assistance.
      6. Search up and down the line, for a maximum of 2 stations in each direction.
      7. If you wish to search away from the guideline, then securely attach your safety spool to the guideline. Mark the exit direction next to the line joint.
      8. Observe for silt disturbances or percolation from bubbles as you search.
      9. If unsuccessful, tie off your safety spool and return along that line to the guideline.
      10. Leave all lines in place and exit the wreck.  Never remove any line until the whole team is confirmed present outside the wreck.

2.      Lost Line Drill

This drill is used if a diver/s lose the guideline.   Divers should never travel inside a wreck without definite visual or tactile confirmation of the guideline.

      1. Immediately cease movement and observe for the line.
      2. Deploy your safety spool and immediate tie-off at that location.
      3. Using the safety spool conduct an appropriate search for the guideline.
      4. Search must be 3-D, following the outside surfaces of the compartment.

3.      Broken Line Drill

This drill is used in the event that the guideline is severed.  If the exit side of the guideline cannot be observed, the situation should be treated as per ‘Lost Line’.

      1. If both ends of the line are present, then simply tie them securely together.
      2. If the line cannot be re-joined, then tie-off the loose ends of the guideline onto nearby objects.
      3. Return to the furthest tie-off on the guideline and use the jump/gap spool to bridge the gap between the tie-offs on either side of the break.

4.      Entangled in Guideline Drill

If a diver becomes entangled in the guideline, use this drill:

      1. Buddy lends assistance to carefully un-entangle the diver out of the line.
      2. If unsuccessful, then the tangled diver will reach to either side and securely hold the guideline with each hand.  (This forms a temporary ‘bridge’ in the guideline).
      3. Buddy cuts the guideline on either side of the tangled diver (inside where the line is being held).
      4. Tangled diver maintains control of both sides of the line.
      5. Buddy performs the Broken Line Drill.
wreck diving techniques

When it comes to wreck penetration – “If in doubt, stay out”.

Diving in Overhead Environments – Fatal Incident Analysis

Whilst sobering, the following analysis findings illustrate the key human failures that have led to actual diving fatalities.  Within every fatality report concerning deaths in overhead environments, one or more of the following errors was present:

Failure to understand that open water training is insufficient for overhead diving environments.  Not obtaining proper training.

Failure to maintain a continuous guideline to open water.

Failure to properly manage air supply by violation of the ‘Rule of Thirds’.

Failure to understand personal limitations by exceeding experience and training.

Failure to provide adequate light (primary + 1-2 back-ups).


 For details about my specialist wreck diving courses, please see:

PADI Wreck Diver

Overhead Protocols

Technical Wreck

Sidemount Diver

Wreck-Diving Lessons Subic Bay Philippines


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