Wreck Diving Risks: Hazards, Dangers, and Precautions
Wreck diving is a popular activity that is enjoyed by scuba divers all around the world. Wrecks are a particularly fascinating dive site and attract divers due to their history and the ecosystem they attract; a dazzling diversity of marine fauna and flora. However, wreck diving is not without hazards, especially when scuba divers enter a shipwreck. As a passionate wreck diver and technical wreck instructor for many decades, I have encountered all of these wreck hazards personally. In this article, I will give a detailed explanation of the wreck diving risks, and provide insights into how to avoid or mitigate them.
What is Wreck Diving?
Wreck diving is the exploration of sunken ships or other human-made structures underwater. These wrecks can be found in oceans, seas, and lakes worldwide, and they often provide an ecosystem for various marine creatures. Wreck penetration diving is an advanced scuba activity that requires specialist training and equipment to stay safe. Wrecks can be hazardous due to their overhead environment, disorientating layouts, and silt build-up.
Is it dangerous to dive inside wrecks?
Entering a shipwreck requires specialized wreck diving equipment and training. Moreover, wreck penetration poses a number of very specific risks that wreck divers need to be aware of. The following are some hazards associated with wreck diving: the difficulty performing scuba emergency skills in an overhead environment, getting lost or disoriented, getting entangled in guidelines, cables, or electrical wiring, injuries from the wreck structure or marine life, and losing vision because of a silt out or light failure.
In order to safely explore inside a shipwreck, it is necessary to have comprehensive wreck penetration training from an expert specialist advanced wreck instructor. This additional training, as well as the requisite specialist equipment, is essential to mitigate wreck diving risks and safely explore the dark and often silt-filled compartments of a shipwreck.
What are the wreck diving risks?
Wreck diving poses six risks that are not present, or as severe, in open water scuba diving:
- Overhead environment
- Silt out and zero visibility
- Environmental hazards
- Marine life injuries
When wreck divers penetrate into a wreck they enter an overhead environment. Prominent among the wreck diving risks is that divers cannot ascend directly to the surface once they have entered the wreck. The dark corridors and hatches of a wreck can be very enticing, but venturing inside can all too easily turn sour. Losing the ability to immediately head for the surface takes away the single most effective survival option when a scuba diving emergency happens.
Entering a wreck can also make the emergency responses you were taught as a scuba diver ineffective. If a gas supply depletion or regulator failure emergency occurs, conventional buddy breathing or air-sharing methods may not be possible in the tight confines of a passageway. Wreck penetration divers must use specialized dive equipment and more advanced techniques to mitigate those wreck diving risks; what you learned during entry-level diving certification simply isn’t enough.
Before beginning a wreck penetration dive, divers must calculate their air consumption at depth, taking their cylinder gas volume and breathing rate into account. A redundant air source, such as a pony bottle, sidemount system, or double tanks, with an extra-long hose on the regulator is considered a prudent necessity for wreck penetration divers. Proper dive planning includes each wreck diver retaining a calculated gas reserve for exiting the wreck, ascending, and making a safety stop, whilst donating gas to a buddy.
Navigating inside a wreck when the floor, walls, stairways, and hatches are at counter-intuitive angles can be disorienting. A shipwreck will deteriorate over time, compromising its integrity, changing its layout, and potentially making wreck navigation even more challenging. Equipment can break loose, bulkheads can collapse, and doors can rust shut, blocking passageways and making obvious exit routes impassable.
It can be easy to unknowingly change deck levels, blunder past a junction, or get turned around and not remember the way out. Using a wreck reel to lay a guideline provides a clear path back out of the wreck. In limited visibility, proper deployment of a wreck guideline can be the only thing to get you safely back to the exit.
Silt out and zero visibility
Deep inside a wreck, there is often no ambient light and very little water flow. In these conditions, fine, dust-like silt thickly covers the floor and builds up on all surfaces. When unintentionally disturbed, that silt billows into the water and decreases visibility to zero. That is known as a Silt Out.
It’s essential not to touch anything inside a wreck to help avoid silting out. In the tight confines of a silt-filled wreck, even a diver’s exhaust bubbles hitting the ceiling can decrease visibility. Whilst advanced wreck divers are trained to a very high level in fundamental wreck diving skills, such as precision buoyancy, horizontal trim, and non-silting propulsion techniques, they are also keenly aware that silt out can be unavoidable.
Another cause of zero visibility is dive light failure. If the diver’s torch stops working, they are not able to see around them, signal their team or read their gauges. For this reason, recreational wreck divers are limited to staying within the ‘light zone’ of a wreck; where ambient external light always illuminates the exit. Technical wreck divers, who venture beyond the light zone, will always carry at least three dive lights; a primary light and two reliable backups.
Consequently, experienced wreck divers diligently train and practice in simulated zero visibility to ensure safety when the worst happens. They become adept in advanced wreck skills like; touch-contact communication, following the guideline without sight, searching for a lost guideline, or finding a missing dive buddy in zero visibility.
Wrecks are often favorite fishing spots, and fishing lines and nets get caught on the exterior of a wreck. Monofilament fishing lines can be almost impossible to see in certain conditions, and it is easy for a wreck diver to get tangled in them. Inside wrecks, there may be cables or loose electrical wiring hanging from the ceilings and furnishing fabrics floating around compartments. These hazards can be dangerous, potentially causing entanglements that trap divers on the wreck.
As wreck rusts and deteriorates, pipes and other fixtures, once hidden in ceilings and walls, can come loose and snag on a wreck divers’ equipment. Divers, or even just their rising bubbles, might accidentally dislodge objects that can fall and entrap them.
Specialist wreck penetration training helps you recognize potential entrapment hazards and teaches you how to remove a snag on your equipment or safely use a cutting device to free an entanglement without panicking. Comprehensive training and experience using a wreck penetration reel will help protect you from another significant entanglement hazard: getting wrapped up in your own guideline.
As wrecks inevitably rust away, wickedly sharp edges can form on the metal structure. Wreck divers may also encounter sharp encrustations, such as barnacles or sea urchins, or irritants such as fire coral. These wreck hazards cause the risk of cuts, abrasions, lacerations, splinters, and contusions.
The best way to avoid these wreck diving risks is by developing robust diving fundamental skills to avoid contacting the wreck.
A secondary measure to prevent wreck diving injuries is to wear full-body exposure protection. Even in tropical waters where thermal consideration isn’t necessary, a dive skin or 3 mm wetsuit will protect wreck divers from scrapes and cuts caused by inadvertently bumping the wreck. Some experienced wreck divers also wear protective diving helmets.
A further wreck diving risk posed by the environment is that of toxic chemicals and contaminated water. Most wrecks are created when ships sink unexpectedly; through accidents, storms, or in military conflicts. Those vessels invariably contain large quantities of oil, petroleum, lubricants, and other chemicals. Some carry hazardous cargo. Military vessels can contain explosives and ammunition. The toxic remains of dangerous chemicals, including solvents and lead-based paints, could be hidden in the silt and mud of a wreck, diluted into the water, or floating in air pockets.
The best way to mitigate these wreck diving risks is to avoid disturbing silt inside the wreck, don’t put your head into air pockets, and don’t touch or interfere with containers, pipes, or valves inside the wreck.
Wrecks that are deliberately sunk as artificial reefs and scuba diving attractions tend to be a lot safer. They are diligently cleaned of contaminants before sinking to comply with local and international environmental regulations. These wrecks are usually also prepared for increased diver safety by removing loose objects, removing hatches, and cutting numerous extra large access points through walls and the hull.
Marine life injuries
Wrecks attract a high concentration of marine fauna and flora, and some of these aquatic species can be a danger to divers. Hazardous marine life risks can, and should, be avoided as you would on any scuba dive.
However, some marine life injury risks are increased when wreck diving. Venomous fish like Scorpionfish and Stonefish can be near-invisibly camouflaged on the walls and decks of a shipwreck. Moray eels can hide in pipes. Urchins, fire corals, and stinging hydroids cover the outer surfaces of wrecks. Lionfish naturally congregate in open hatchways. Some wrecks attract predatory sharks, giant barracuda, and sea snakes.
As a wreck diver, it is important to pay close attention to your surroundings. Be observant of marine life and don’t seek to interfere with it. Anticipate imperceptible dangers on the walls and surfaces of wrecks; use good buoyancy and maneuvering skill to avoid making accidental contact with the wreck.
Mitigating wreck diving risks
Wreck diving is an exciting and alluring activity for many divers who are attracted by the unique ecosystem and photo opportunities found in sunken ships. However, it’s important to remember that safely entering a shipwreck requires specialized equipment and advanced training.
Improve core diving skills to reduce wreck diving risks
The first step in mitigating wreck diving risks is to develop your core scuba diving proficiencies;
- Precise buoyancy control
- Streamlined horizontal trim
- Efficient propulsion techniques, such as frog kick
- Maneuvering skills, such as helicopter turns
- Situational awareness
- Gas management and planning
- Team diving and buddy-system skills
- Refreshed and reliable emergency procedures
Many scuba divers neglect to develop these fundamental diving skills, instead seeking more glamorous higher-level certifications. However, it is these most basic skills that do the most to increase wreck diving safety when they are refined to an advanced level of proficiency.
Comprehensive dive planning to avoid wreck diving risks
Well-strained and experienced wreck divers create comprehensive dive plans, with high attention to detail, that assume worst-case scenarios will occur. Gas consumption and no-stop limit calculations will be factored into that plan. There will be an agreed contingency plan for each of the foreseeable wreck diving risks.
When an emergency does occur, scuba divers will respond far more effectively if they have an existing plan in mind. Having a detailed plan to follow also helps with stress management. Divers tend to panic when they feel threatened and don’t know how to save themselves.
Specialist procedures for wreck diving risks
The second step to mitigate wreck diving risks is to learn the specialist emergency procedures for wreck diving. These deal specifically with situations like silt outs, divers lost inside the wreck, entanglements, light failures, and air-sharing through confined spaces. These procedures, skills, and protocols are typically only taught on advanced wreck diving courses by highly specialist and extremely experienced wreck diving instructors.
Specialist equipment for mitigating wreck diving risks
Advanced wreck penetration divers have learned from experience to use specialist wreck diving gear to mitigate these wreck diving risks and increase their safety when exploring explore dark and silt-filled compartments.
Specialist wreck diving equipment typically includes:
- Redundant cylinders and regulators.
- A 2m/9′ long hose for air-sharing in tight spaces.
- A powerful primary torch and two backup lights.
- A large wreck reel for laying guidelines.
- Safety spools for emergency search procedures.
- Protective helmets for impact protection.
- Cutting devices and backup cutters.
This special wreck diving gear cannot be utilized effectively without the training necessary to implement it into established procedures. When seeking wreck diving certification, search for a wreck instructor who introduces this equipment on their course and teaches how to use it within specific risk-focused procedures. The average recreational Wreck Diver course falls far short of providing reliable proficiency in the equipment and protocols for safe wreck penetration diving.
Read more of my wreck diving articles!
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About The Author
Andy Davis is a RAID, PADI TecRec, ANDI, BSAC, and SSI-qualified independent technical diving instructor who specializes in teaching sidemount, trimix, and advanced wreck diving courses.
Currently residing in Subic Bay, Philippines; he has amassed more than 10,000 open-circuit and CCR dives over 30 years of diving across the globe.
He has published numerous diving magazine articles, designed courses for dive training agencies, and tests/reviews dive gear for scuba equipment manufacturers. He is currently writing a series of advanced diving books and creating a range of tech diving clothing and accessories.
Prior to becoming a professional technical diving educator in 2006, Andy was a commissioned officer in the Royal Air Force and has served in Iraq, Afghanistan, Belize, and Cyprus.
Wreck diving risks FAQ
There are seven specific hazards in wreck diving:
1. Overhead environment
3. Silt out and zero visibility
6. Environmental hazards
7. Marine life injuries
Diving on wrecks has the same hazards as normal scuba diving, but also more severe risks of entanglement, disorientation, and the inability to immediately ascend if the wreck is entered.
Sunken wrecks often contain volumes of petroleum, oil, lubricants, and other toxic chemicals. Some vessels sink whilst carrying a cargo of hazardous contaminants. Military vessels may contain ammunition and explosive ordnance.
Dangerous marine fauna and flora can cause envenomation, stings, bites, lacerations, scratches, contusions, abrasions, and penetrating wounds. Marine life injuries have a higher risk of infection.
Wreck divers can become disorientated and get lost from the exit. Silt can be disturbed causing zero visibility. Loose cables and wiring can entangle divers. The wreck structure can collapse, crushing divers or trapping them inside. Divers cannot immediately ascend if they suffer an equipment failure or run low on gas.
Improving fundamental diving skills, like buoyancy, trim, propulsion, and situational awareness, allows most hazards to be avoided. It is prudent to carry a redundant gas supply and create detailed wreck dive plans; including gas consumption and contingency plans for worst-case scenarios.
A silt out occurs when a scuba diver unintentionally disturbs fine silt and sediment which clouds the water and creates zero visibility. Silt outs occur frequently when wreck diving inside confined areas of shipwrecks.
An overhead environment is defined as an area with no direct vertical access to the surface. Cave, cavern, and wreck penetration diving are examples of overhead environments. Specialist training, equipment, and procedures are needed for diving in overhead environments.
A redundant gas source is a separate cylinder and regulator carried by divers to provide a higher level of safety if an equipment failure occurs. Examples of redundant gas sources are; pony cylinders, sidemount systems, and manifold double tanks.
The four main reasons why divers get lost inside shipwrecks are:
1. Impaired situational awareness
2. Weak navigation skills
3. Disorientation in confusing wreck layouts
4. Disturbing silt and sediment to cause zero visibility
Wreck penetration causes fatal diving accidents when divers drown because are unable to exit a wreck due to disorientation, zero visibility, entrapment, or entanglements. The same factors can cause delays in ascending which can result in gas depletion or decompression sickness (DCS).
First improve your fundamental diving skills, like buoyancy, trim, propulsion, situational awareness, and dive planning, to a high level. Then seek a basic Wreck Diver certification course with an expert wreck specialist instructor. To safely penetrate wrecks, gain an Advanced Wreck Diving certification.
I can relate to your experience. At tech diving levels, there seems to be a disassociation between getting trained for depth and getting trained for wreck penetration. The uptake of technical WRECK courses is far smaller than that for general tech certification. A lot of tech divers seem to convince themselves that they’re somehow innately prepared and able to operate safely in overhead environments. That’s probably why the cave community is historically so dismissive of wreck divers. Even when tech divers do undertake a technical wreck course, I’ve noticed that a lot of those courses are more fixated on simply visiting wrecks at depth, rather than delivering any sophistication in best practice skills and procedures for overhead environment diving. I can understand why some tech divers don’t feel technical wreck training is a necessity; many courses don’t deliver exemplary penetration skills, and the mindset of not requiring specific advanced training to enter wreck has become widely normalized across the tech diving community.
My worst experiences were- Stopped to photograph an electric fan at around 56m, looked up into darkness, my guide was gone, only a good canister tech light found a reddish patch were divers had polished the steel leading to the next compartment were I found my guide entering the next compartment. I was his ghost for the reminder of the Gauntlet dive, this was 2012. Another experience was a 7 1/4 minutes in an ER staircase at 56m. The guide finally got me out. I was so worried about a lens scratch, the video still chills me. The video is blank with just my breathing, trying to get to 3 breaths per minute, a total fail. Both Air doubles. Cheers, I really appreciate your posts to make diving safer, back to Chuuk in June for another 30 dives…