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Big Blue Tech - Koh Tao - Thailand                                                             Facebook  Twitter  GooglePlus

Wreck-divingDivers or non-divers, most people are fascinated by the idea of a shipwreck. On hearing the word, many will think of smugglers, galleons, battleships, or a famous oceanliner sunk in tragic circumstances, such as the RMS Titanic.

Reading about them or watching a documentary is about as close as most people will get to seeing one, but for divers there is the very real prospect of exploring many different kinds of wrecks in established dive sites all over the world. Diving around the outside of a wreck can be exhilarating, eerie, or even scary, but for the most part, done safely- with training. Recreational wreck diving speciality courses introduce divers to procedures for navigating around the outside of a wreck, and provide basic information on how to research or find a wreck. But with the exception of the SDI course, they are not designed to allow a diver to go inside a wreck, and this is emphasised throughout the PADI and SSI courses (even though the PADI course does include very limited penetration).

Exploring the inside of a wreck requires training, practice, and patience. They are very dangerous places to be in. Hazards include loss of orientation due to a “silt-out”, entanglement on fishing line, net or electric cables, entrapment due to collapsing structures such as a ceiling or unsecured hatch, and rapid changes to diving conditions due to encroaching bad weather during a dive.

People who scoff at these hazards are often the ones that think “that will never happen to me, I know what I’m doing”. They are usually also the divers that end up getting killed, or, even worse, lead someone else inside a wreck and get them killed.
As a TDI and SSI technical dive instructor, I see this complacent and over-confident attitude all the time. We have a very tame wreck in Koh Tao called the HTMS Sattakut. It’s an old landing craft infantry vessel, and was involved in numerous battles in World War 2. It was sunk in 2011 to act as an artificial reef, and is dived daily on the final dive of the SSI advanced adventurer or PADI advanced open water course. It’s also a daily occurrence that instructors or divemasters can be seen exiting the wreck with no torch, no guideline, little or no exposure protection, and anything from 1 to 6 students or customers following behind them. Now the Sattakut has been stripped of its engines and furniture, and it has a lot of natural daylight on the main corridors, so it’s unlikely that you will get yourself into any real trouble (apart from the potential for panic) unless you go into the lower levels. But that’s not the point. The point is that bad dive professionals are instilling into those students or customers a false sense of security that all wrecks are like this, and they may go to another wreck somewhere (with or without a dive guide), copy the same methods to penetrate, quickly find themselves in serious trouble and not have the means to deal with it.

Diving fatality reports are very sobering reading. Type the word wreck into the 2013 BSAC annual diving incident report and you will see that there are more than 50 incidents involving wrecks, many of those fatal. The most common reasons that people die when diving wrecks are due to:

  • Failure to obtain proper overhead environment training.
  • Failure to maintain a continuous guideline to open water.
  • Failure to properly manage gas supply.
  • Exceeding personal experience and training.
  • Failure to provide adequate lighting.

Let's briefly look at just one hazard of diving in an overhead environment; disorientation due to lack of visibility caused by a silt-out. The way I describe it to my wreck and advanced wreck students is to imagine visiting a ship in a maritime museum. Go inside it, down a few flights of stairs and walk along the corridors until you find a room. Now cover your eyes, spin yourself around a few times and feel your way out (you could also try it at home- go to the bathroom with your eyes closed the whole time after spinning around!). You’ll get out of the ship eventually, but it will take a long time and you’ll probably have a few bruises on your head and shins! Now imagine the same thing underwater but remember the following- you have a finite amount of gas, the ship may be on its side or upside-down, if you bang your head you could knock yourself unconcious or begin bleeding, you may be going deeper into the wreck and you may get tangled up and/or entrapped at any point. If you wish to penetrate wrecks, then these are the things you need to be trained to deal with. I make a point of showing my students on both the SDI wreck course and TDI advanced wreck course a complete silt-out. For the SDI students, I get them to stay at the exit whilst I stir up silt. Within seconds both I and my powerful canister light have completely dissapeared. For my advanced wreck students, they need to experience being inside that cloud of silt. 

Summary of advanced wreck training
In the same way that you’re probably not going to go for a dive to 30m immediately after the pool session on your open water course, you’re not going to explore the deep dark recesses of a wreck without gaining the appropriate skills and experience. Advanced wreck courses are designed to give a diver the tools that they need to minimise risk. They also teach and allow practice of skills that could save your life if, for example, you suddenly found yourself swimming through a thick cloud of silt. The TDI advanced wreck course runs through the following:

Gas management- In any overhead environment, you should calculate the amount of gas you will need, and also allow for any contingencies, such as two people having to share air from their furthest point of penetration to either the surface, or the depth of their next breathable gas (rock bottom or minimum gas), say a switch onto 50% O2 at 21m. You will also need to decide what rules to use for your gas contingencies (e.g. multiply deco gas requirements by two for a buddy team of two, x1.5 for 3 or more divers). The basic rule of thirds does not work on back-gas in a wreck, not with one person out of air and two elevated breathing rates. Go through the maths yourself, it will get you killed.
If the dive is a decompression dive you may also be carrying deco cylinders that will need to be staged securely before penetration, somewhere near the entrance point, then found and retrieved on exiting. How you carry your gas also needs to be considered. Will you be using a twinset with an isolation manifold, or independent doubles as in sidemount? Are you diving different sized cylinders to your buddy or buddies? If so turn pressures based on bar is not adequate, you need to calculate volumes. What gas mixtures will you be using- do you really want to penetrate a deep wreck on air have to deal with gas narcosis on top of everything else? If your main gas is trimix is it hypoxic? Will you need a travel gas? All of these factors are covered during the course.

Navigation and reel work- Using a reel is the primary tool for navigating your way inside and outside of a wreck. You will learn about the different types of reel and spools, how to hold them, how to reel in and out without creating a “bird’s nest” or tangling yourself up, how to lay the line and where (securely and not on sharp objects), and how to apply the different types of tie-off to secure the line without it disappearing behind an object that prevents its use on exiting (so-called line traps). You’ll also be taught how to use spools to “jump” from the main line to explore different areas of the wreck, connect a gap between two lines, or use a spool to look for a missing diver or the main line if you (hopefully never) lose it. You’ll also learn ways to mark the line using line arrows to either mark the exit or allow you to look for a missing diver. However, you should also become familiar with the inside of any wreck by progressively penetrating with each subsequent dive, and back-referencing where you are at any point. You’ll also be taught to cover your torch to look for ambient light or your buddy’s light in the event of separation from them or the line.

Team roles and positions- Wrecks can be a bit cramped inside, which usually (but not always) necessitate the buddy team diving in single file. You’ll learn about the different ways for a team to position themselves, and also who will do what during any given dive. Things would get very messy if every member of a team used a reel, so one person will take the role of the reel diver, with the other diver or divers acting as support and taking responsibility for other aspects of the dive.

Buoyancy and propulsion techniques- The way you propel yourself through the wreck will affect how much you can see; if you’re flailing around all over the place, you will reduce visibility pretty quickly and might injure yourself on any sharp bits of metal. Likewise, if your buoyancy is no good, you could be tangling yourself up in your own line or something else, you may puncture your BC, or if you float up to the ceiling be in danger of dislodging your 1st stage regulator. You could also dislodge a piece of the wreck (i.e. the ceiling) and find yourself entrapped. Effective finning techniques and buoyancy skills are fundamental to the course.

Communication- The lower levels of wrecks often go beyond the daylight zone, so simple hand communication is not always adequate. Using the torch to communicate, or in conjunction with hand signals without blinding your buddy are very important skills to learn. Once you have mastered these you can dive very efficiently without having to even stop or turn around to check your buddy is ok (global and situational awareness).

Equipment selection and use- Knowing how much and what type of equipment will make the difference between getting tangled up on every single bit of line you encounter, or finding yourself in need of some piece of equipment but not having it with you. Every dive requires slightly different equipment configurations, and you’ll understand how to choose what you will and won't need for any wreck dive you do.

Emergency procedures- So what if you did silt out the room you are in and now find yourself having to feel your way out? It can be done. It can even be done with your buddy(s) by using touch contact and holding on to that line that you so diligently laid on the way in. It can even be done if someone is suddenly out of air and you having to exit through some tight spots! You’ll learn how and practice until you get it right. You’ll even learn basic communication. Other fundamental skills to master include a lost line drill, catastrophic gas failure, loss of primary light and missing diver.

Entanglement and entrapment- Developing good self, global, and situational awareness will help you to minimise the likelihood of getting entangled or entrapped, but lines and cables have a mind of their own and in bad visibility it could happen (or in good visibility if your concentration slips). Again, you will learn effective techniques for dealing with such situations on yourself or your buddy.

The above is a lot to take in, which is why it is called advanced wreck. To undertake the advanced wreck course you must already have a wreck specialty qualification. The SDI wreck course provides a foundation to build from. However, you'll also be much better placed to successfully complete the course if you are already a technical diver to the level of decompression procedures or higher. The TDI advanced wreck course is comprised of classroom sessions, land drills and a minimum of 6 penetration dives, that allow you to understand and practice all of the above skills and techniques. It will make you more aware of the risks of wreck diving, allow you to plan and execute penetration dives, and enable you to deal with any reasonably foreseeable issues you may encounter. You will challenge yourself, you may learn a little bit about yourself, and hopefully you’ll have a lot of fun throughout as well!

Richard Devanney

If you’re interested to find out more about advanced wreck training, contact us at This email address is being protected from spambots. You need JavaScript enabled to view it.

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