Wreck Speciality course DJL diving

Davy Jones Locker instructor Dani recently took one of our Divemaster candidates Kieran through his wreck speciality course. Following that she has written a new article for the DJL Blog containing some great wreck speciality advice. Wreck exploration and penetration is one of the most exciting aspects of diving. However it does have some inherent risks and dangers that divers need to be aware of.

Wreck Speciality course DJL diving
Danis Wreck speciality tips

One of the most exciting aspects of diving is exploring wrecks. But during your open water training you were no doubt constantly reminded how dangerous entering a wreck or an overhead environment is. These are real and significant dangers regardless of your level of diving certification. There are risks present which can impact inexperienced divers and also professionals with years of diving experience behind them.

Cave or wreck?

• There are a multitude of differences between caves and wrecks. Caves may seem to be more dangerous as they usually only have one exit. Wrecks on the other hand often have a number of entry and exit points. This may lull divers into a false sense of security about possible risks. A greater number of exits can appear to make a wreck seem less dangerous. This is not always the case however, in a cave there will typically be a current flowing outwards. This current is useful for helping divers return to the cave entrance. Once inside a wreck there is nothing similar to assist an exit, only dangers which can result in divers getting trapped inside.

Why should I get my Wreck speciality?

• Before you enter any wreck you should obtain wreck diver training. A wreck speciality course will help you start appreciating the additional hazards that are part and parcel of wreck penetration dives. But what is so fascinating to divers about entering a sunken wreck? The reasons are numerous and varied. It It may be that after catching a glimpse of a dark entrance there is a temptation to explore inside. However “just taking a look” can lead to entering a wreck without the correct training which is potentially fatal. However, with the correct training it doesn’t take long for divers to able to navigate these dark passageways safely.

• The definition of wreck penetration is to enter any area that does not have direct access to the surface. This includes a quick entry to look around followed by an immediate exit. In any situation where even the smallest penetration may have taken place a line showing the exit route should be laid. Line laying is a technique that experienced divers can become very adept at. It must be included as part of every dive involving the penetration of a wreck.

Wreck Speciality course DJL diving


The following safety protocols must be adhered to

1:  Areas that two divers are unable to access side by side must be avoided.

2: Gas managements’ rule of thirds must always be followed.

3: Removal of equipment is forbidden while inside an overhead environment.

4: The above guidelines apply to all overhead environments and divers must adhere to them at all times.

When divers enter a wreck an attachment is made with the guide line at 2 places. These are known as primary and secondary tie offs. It is standard procedure to replace an old line by laying a new one if it looks worn or damaged.

Propulsion techniques

• It is always advantageous to have clear water when exiting a wreck. Using a good propulsion technique helps maintain an environment where visibility is relatively good. The “pull and glide” method is a technique many divers prefer as it preserves visibility.

If the a corridor inside a wreck is large enough then divers might use a frog kick or modified flutter kick. Using these kicking methods means that the power from the fin kick goes backwards. This is better than kicking up and down which may kick up silt and affect visibility. Perfect bouyancy control is necessary when kicking behind you to prevent yoursellf sinking to the floor.

Hazards of silt outs

• Regardless of the fin kicking style you use, silt can be potentially fatal. It will rear its ugly head at every chance. The definition of silt is particles occurring in the water which can affect visibility during a dive. It can be either manmade or natural, i.e. particles of rust or clay. The types of silt divers encounter in a wreck do vary. They include;

1. Sand grains: are the least serious and can settle very quickly.
2. Mud: A bit more serious, because it is easy to disturb and may take a long time to settle.
3. Clay: More serious, easy to disturb, takes hours to settle, sticks to anything
4. Volcanic ash: While not exactly common, proves a serious problem due to magnitude of deposit and fineness of particulate. Some popular sites in the Philippines are notoriously bad and up to a metre of ash can be deposited in some places.
5. Man Made: Due to the many types of substances used in ship construction, the following are included: Rust particles, expanded foam or wooden panels, hardboard and carpet fibres. Oil /fuel residues, becoming re-suspended, Coal dust etc

Wreck Speciality course DJL diving

Wrecks lay in all manner of positions on the seabed; it would be very difficult to say where most silting would occur. In areas of suspected silt build up it’s advisable to keep closer to the guideline. Circling it loosely with your thumb and forefinger where visibility is limited. When entering an enclosed area which may contain silt it is best not to touch anything and keep an eye on where you are going.

Keep your group small

Wreck exploration is always more practical with a dive buddy, but not a dive party! The buddy behind can illuminate possible line placements and assist with any entanglement issues.  Visibility gets poorer as more people enter an overhead environment and this will have a dramatic effect on group safety.


Always make sure you stream line equipment with no danglies. Keep spare masks, back up knives and tools in pockets, (but remember back up lights are never put in pockets).

Communication Methods

Wreck spec advice1. Tactile signals can play a big part inside a wreck. Even with the brightest, high grade dive lights and back ups, if the visibility is nil then they are useles. There is now a touch contact system that allows a team of two or more diver to exit quickly and safely. Don Rimbach, a well known Cave Diver, came up with this method to help groups of divers exit an overhead environment. This method uses squeeze signals. The lead diver stays  on the guideline waiting for the diver behind to make contact (preferably above the knee ). Next the second diver will PUSH ONCE to GO. To stop the exit the second diver will SQUEEZE ONCE and the lead diver will wait. To back up the second diver will PULL BACK on the lead divers’ leg.

2. Finally, consider a situation where you and your buddy are following a line. Visibility is zero and you reach  a “dead end” where you need to turn around. In order to deal with this situation you and  your buddy will need to discuss an effective touch system.

3. The hand signals below show some new signals peculiar to the overhead environment. There are similarities with these signals and those used in Cavern and Cave diving. Divers use control signals such as “OK”, “HOLD” and “EXIT”. The recipient of a control signal will mirror the signal back to the person who sends it. This confirms that that they understand the signal they receive.

wreck spec advice

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Ending the dive for ANY reason

When diving in an overhead environment, a diver can abort the dive at anytime and for any reason. Entering a wreck can be dangerous if, on a particular day, you don’t feel relaxed or confident. In these circumstances it is always better to abort a dive.
As you swim through the wreck it’s important to be aware that the dive maybe finished by any of the team.  Reasons for this that may not be obvious but if a diver isn’t comfortable then it is safer to abort.


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