Experience or stupidity may get you there...
inspired training will get you back!


Technical Diving Articles



STAY OUTSIDE! For many divers the greatest thrill is exploring ship wrecks. But, as you progressed through your open water training, you were no doubt constantly reminded about the dangers of entering wreckage or any overhead environment. The dangers are real and valid whether you are a relative new comer to diving or a seasoned dive professional with many thousands of dives. Overhead environments take various guises, but more divers obtain cavern and cave training nowadays over wreck.  Although similar, caverns and caves are hardly as challenging or as interesting as swimming through the twisted and sharp confines of the sunken museum.


The differences between cave and wreck are many.  Caves have generally one exit and this makes them seem dangerous. Wrecks, however, appear to have many, and this leads to diver complacency and failure to obtain training. The cave typically has an out flowing current to help your exit, whereas the wreck offers no assistance or consistency and actively seeks to entrap you with its rusted metal claws.

Before you enter any wreck you should obtain Advanced Wreck diver training which will help you start appreciating the added hazards that go hand in hand with your trips into the magnetic overhead environment. Proper training will provide in- water skill building focussing on the emergency drills needed to safely exit should trouble occur.  On completion of training, you will be able to cast off your “open water safety wheels” and enter the most hazardous of the underwater domains…the rusty shipwreck. There are many reasons to go inside a wreck.  Many of you will, no doubt, have prematurely been attracted to the darkness and ventured where you shouldn’t. It is very alluring to stick your head in and before you know it your whole body is propelling you into a possible early grave.  However, after as little as 5 days training you can safely penetrate these passages and live to tell the tale. Think of advanced wreck training as a sub aqua prophylactic helping prevent  unwanted complications!

Wreck Penetration by definition means going into an area where direct access to the surface is not available. Even a brief “look see” means you have penetrated the wreck and should have laid a line to show your exit route. Wreck penetration should always involve line laying, and good line technique is an art in itself. Wreck penetration techniques are beyond the limits taught in a standard wreck course.

Standard wreck courses, often called a specialty course, offer an insight into wreck history, focus more on basic mapping and offer very little in line laying or actual overhead environment experience. These speciality courses are aimed at the relatively neophyte diver who seeks more interesting dive destinations without the hazards and dangers of entering the overhead environment. Typically, a linear distance to the surface limit is imposed of say 40m, which means that a wreck laying in 35m allows a maximum penetration of 5m. An Advanced wreck course generally has a maximum depth limit of 50m while breathing air, but it would be advisable to use trimix inside wrecks deeper than 30m.

There are no restrictions on penetration other than adhering to the following safety protocols:

1: No entering areas that two divers cannot enter side by side

2: 1/3 rd's gas management protocols adhered to

3: No equipment to be removed within the overhead environment

4: Guidelines to be used, in all overhead environments.

When entering a wreck the guideline will be attached in two places called the primary and secondary tie offs and you should always lay a new line if you suspect an old one. Unlike the tourist caves of Florida or Mexico the wreck diver will not have the luxury of simply following a permanent guideline.

A good propulsion technique will ensure you have relatively clear water to exit in. Many experienced wreckers simply use a pull and glide technique as this tends to preserve the visibility. There are some awkward skills to master, what with laying the guideline sensibly and holding your dive light all while navigating the wreck and avoiding silt outs.

Silt is a potential killer while wreck diving and no matter what your fin style, Silt will rear its ugly head at every chance. Silt is defined as particles occurring in the water, and due to their suspension, affecting visibility during the course of the dive. Silt can be either manmade or natural, i.e. rust particles or clay particles. There are various types of silt you may encounter in a wreck, these include:

Sand grains: the least serious, generally falling out of suspension very quickly.       

Mud: A bit more serious, because it is easy to disturb and may take a long time to settle.

Clay:  More serious, easy to disturb, takes hours to settle, sticks to anything

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 suffer very badly, with ash deposits almost a metre deep in places

Man Made:  Due to the many types of substances used in ship construction, the following are included: Rust particles, carpet fibres, hardboard, and wooden panels, expanded foam panels. Oil /fuel residues, becoming re-suspended, Coal dust etc

Wrecks lay in all manner of positions on the seabed; it would be very difficult to say where most silting would occur. With floors becoming ceilings and sidewalls becoming floors, its best just to watch where you are going, and use the most suitable propulsion techniques. In areas of suspected silt build up, it would be prudent to maintain a closer position to guideline, often maintaining a “loose ok” sign where visibility is compromised. A good approach to entering a silty overhead environment is to touch nothing and watch where you are going!

Wreck exploration is better accomplished with a dive buddy, but not a dive party!  The buddy behind can illuminate possible line placements and help with any wreck entanglement problems. The bigger the group that enters the wreck the poorer the visibility and this will have a dramatic effect on group safety.

If the size of the corridors inside allows, divers may wish to use a frog kick or modified flutter kick. These types of kicks direct the power of the fin kick backwards and not up or down which will help maintain visibility. With the fin power directed behind, you should obviously have perfect buoyancy control or you will find yourself constantly falling to the floor!

Apart from the dangling stuff, this diver shows good horizontal trim

Early sorties into a wreck should be limited to the no decompression limits, until your experience and subsequent training allow for more adventurous penetrations. Any decompression cylinders should be clipped off just inside the primary tie off point, as they would drastically increase entanglement risk.  The use of Rebreathers inside the narrow confines of a wreck is also to be avoided as they are huge line tangles waiting to happen.

To safely proceed through a multi deck shipwreck requires a series of dives each designed to fulfil a single objective. The early dives should focus on map building and reconnaissance. As a greater knowledge is built and guidelines extended, the dead end areas of the wreck can be eliminated and the desired destination more quickly reached, whether it’s the engine room or the purser’s office.

Equipment should be stream lined with no danglies. Spare masks or back up knives or tools should be kept in pockets, (but back up lights are never put in pockets). A rusty wreck tentacle will actively attract the ill prepared wreck diver, and often, sadly leads to an indefinite bottom time!

Unlike a cave, wrecks have no out flowing current to impede your entry progress. Therefore there will be nothing to assist the exit either. This had led many cave trained wreck divers miscalculating the exit time and gas reserves. Any good training course will have an extensive kit shaping session. The equipment will have all first stages routed “hoses down”, to avoid damage. Manifold use must be mastered in a hovering horizontal position. If greater depth necessitates helium use and therefore suit gas in an argon bottle, much thought needs to address the bottle placement. On the mixed gas train of thought, divers should routinely lower their equivalent narcotic values when planning a wreck penetration, to increase alertness in a stressful situation.

Primary Reel with Back up light attached to assist during exitThroughout the wreck, divers should be visualizing the exit they came from and any closer exits as they emerge (If decompression tanks have been left by an entrance then this is the only exit). Finding safe and interesting wrecks to explore is difficult and time consuming. The skills learnt on a wreck training course, are easy to remember but very difficult to do smoothly without constant practice. During Advanced Wreck training you will get familiar with line laying into the wreck and being a competent buddy. Once line laying skills are perfected, you get to hone your emergency skills. Exiting while air sharing, via a long regulator hose seems quite straight forward, until, you add a buddy with questionable buoyancy and some depth changes. In any situation like this you will try to stay as calm as possible and always swim at a pace that does not elevate either divers breathing. To add some additional spice to the training, your instructor will have you navigating the wreck will your eyes closed to simulate poor visibility and may combine this with air sharing also!

Tactile signals can play a big part inside a wreck. You may have the brightest, most expensive dive light there is, and two back ups, but if the visibility is nil then they won’t help you… A touch contact system has been devised that allows a team of two or more to exit safely and quickly. Devised by Don Rimbach (well known Cave Diver), as a means for several divers to exit an overhead environment. This method uses squeeze signals. Lead diver waits on guideline for diver behind to make contact (above knee preferably). Second diver PUSHES ONCE to GO. To stop exit Second diver SQUEEZES ONCE  (lead diver waits). To back up second diver PULLS BACK on lead divers leg


 In a low visibility situation, dive team members find guideline immediately. Lead diver waits for next diver to make contact either just above knee or maybe divers bicep area. When team is assembled last diver “Pushes” next and so on and group exits maintaining “Loose OK” on the line until visibility improves. In the event of an entanglement diver “squeezes” the next to signal stop. Should a diver need to back up,  he simply “Pulls back” with his hand. Group should wait until problem is fixed and “Push” squeeze is felt to continue. All team members should maintain contact at all times when visibility is compromised. This skill should be practiced often.

Never pull on the guideline

Finally, imagine you and your buddy, in zero visibility, are following a line and you encounter a “dead end” and need to turn around. Discuss with your buddy a suitable touch signal you could use to achieve this

 An Advanced wreck course is a mostly practical experience, but for completeness a thorough course will have a training manual to cover the basics and give a reference source for the material. Although very little of use has been written in the way of wreck diving techniques, my own guide to Advanced Wreck Diving  provides a fresh and innovative way of mastering the academic phase of wreck diving.

 There are various new light and hand signals to learn, these signals are very similar to any used in the total darkness environment.

Pictured below are the special hand signals particular to the overhead environment. Standard open water hand signals are not included. If in doubt standard hand signals should be reviewed with your Instructor

The above hand signals show some new signals peculiar to the overhead environment. These signals are very similar to those used in Cavern and Cave diving. The signals for “OK”, “HOLD”, “EXIT” are control signals. They are to be mirrored back to originator to make sure that they are understood.

 When in any overhead environment, any diver can call the dive at anytime for any reason. Never succumb to peer pressure and enter the wreck if you don’t feel “up to it”. All divers have differing performance levels that vary from day to day.

  As you swim through the wreck, accept that the dive maybe finished by any of the team for reasons that may not be obvious.

To enrol on an Advanced Wreck Course, the pre requisites are a recreational wreck or cavern speciality ticket along with 50 dives. A very useful pre qualification would be nitrox and or decompression diver, as these will enhance the experience greatly. The course should typically include 6 dives inside proper ship wrecks not sterile McWrecks. As with any advanced diver training, your instructors experience is invaluable (check they have some) .Before shelling hard earned cash over, always check out the training sites on a fun dive, ensuring that the overhead environment is actual and not virtual! You owe it to yourself to ensure that the training you receive has value and will prepare you for dives unsupervised. Guided wreck penetration is very rare. Inside a wreck is the last place for an ill prepared badge collector!



  For more details of the full Advanced Wreck Diver Manual...CLICK HERE


copyright Mark Ellyatt