The Hazards of Wreck Diving

wreck diving

As you are swimming along the reef you notice a large dark spot in the endless blue appear. As you start moving towards it, it gets bigger and bigger until you can start to make out some of its features. A large barrel sticking out, a chimney towing above you, railings peeling off and some scattered on the sand around you. You have just encountered a wreck underwater.

For me wreck diving is one of the most fascinating underwater activities, there is always a story behind what happened there. The history that goes with not just the sinking but also the life of the vessel before the sinking. Was there a war or was it just an accident, or maybe on purpose? For many people diving on shipwrecks can bring up different emotions, I have had students refuse to go near one as they said it gave them an eerie feeling, others are too keen and have tried (and failed) to swim straight inside.

There are many amazing wrecks to see you there, and unlike coral reef, which usually sticks to the warm waters of the tropics, you can find wrecks virtually anywhere around the world. In fact you might even have world class wreck diving right on your doorstep. Living in a colder country is no excuse to not go diving you know! Wrecks usually take the form of a boat or ship of some kind, but can also include cars, airplanes, oil rigs, submarines or any other man-made object that shouldn’t naturally be on the seabed.

Wreck diving, although fun and exciting, also has certain risks involved that you do not come across just swimming about over a reef. This is why it is so important to have the proper training and equipment before attempting to penetrate one. Remember that most wrecks are made from metal, and metal corrodes underwater. Over time you will find the outer layer peeling away and forming a razor blade like coated the edge of whatever it is you are diving on. For this reason wearing proper protective exposure suits is very important. This includes gloves, which I normally strongly protest against unless in water cold enough to suit them.

Also wrecks usually make very good artificial reefs, meaning corals and aquatic plants grow very easily on them. Which will inevitably attract fish, which in turn attracts bigger fish. And if this is not a very often dived site, the bigger fish will attract fisherman, who often carelessly drop nets and lines about. Creating entanglement hazards for divers, which is why a dive knife, or preferably 2 is an essential piece of wreck diving equipment.

Entering a wreck has even more and even greater hazards than just swimming outside around them. The biggest of all is that you are now in what’s called an overhead environment. This is a place where there is no longer direct access from the surface, so if anything goes wrong you need to swim to an exit before you can ascend. So you should already have some experience in a range of environments before learning to wreck dive, and make sure you are relaxed and comfortable so you won’t panic inside. Wrecks can be very complex for navigating inside, with staircases up and down, corridors twisting and turning in every direction. For this reason it is essential you take a reel with you. You deploy it before you enter the wreck in a place where you are not overhead. This is called the primary tie off, and then you make a secondary tie off just before you enter the wreck, and then further tie offs every few meters inside, especially when changing direction. It is essential to keep the line without slack as this becomes yet another entanglement hazard. The other reason the most important rule of wreck diving is keeping a line, is because wrecks overtime gather a layer of what’s called silt. Silt is made up of fine particles of mud, sand, rust and many other bits. Silt is usually very fine, and even slightly disturbing this layer can produce an instant loss of visibility, called a ‘Silt Out’. By loss of visibility I mean complete loss, like having parcel take stuck on to your mask. The less dived the wreck is the more silt will be sat on the bottom. This is why having a line is so important, if you can’t see where you’re going at least you can follow your way out. So an important rule of using the line is that you never leave it, be at most an arm’s reach away so if there is a ‘silt out’ you can sweep your arm and grab the line. Then do not let go until you are out!

As well as the nets outside a wreck being an entanglement hazard, inside the wreck can be even more! Most shipwrecks have electrical cabling running through them, which can dangle around making it very easy to get snagged on the yoke screw (one of the reasons why technical divers choose DIN valves over yoke).

These are just a few of the dangers of diving inside a wreck, however don’t let them put you off! You just need to be prepared with both training and equipment. For wreck diving you need a line long enough for your penetration distance, and at least one, preferably two decent quality dive lights (They are usually pretty dark!), A full body wetsuit or drysuit, a pair of gloves, a hood (in case you hit your head), One or two knives (so you can reach them with both hands in case of entanglement), and a slate for more complex communication.

When learning how to wreck dive you should choose a place that has a proper wreck to learn on, it is becoming more and more common for many commonly dived areas to sink ships for the purpose of wreck diving, such as the ‘HTHS Sattakut’ on the diving island of Koh Tao, in Thailand or the ‘Halliburton’ Utila, Honduras. These ships are cleaned out so none or little entanglement hazard, and had anything that could be toxic to sea life removed, such as oil or fuel. These wrecks will give you the best possible training in the safest possible way to ensure you are well prepared for taking on other wrecks.

Safe Diving!

‘The Hazards of Wreck Diving’ was written by Mike

Photo Credit: National Geographic