Davy Jones Locker instructor Dani recently took one of our Divemaster candidates Kieran through his Wreck spec, following that she has written a new article for the DJL Blog containing some great wreck spec advice. Wreck exploration and penetration is one of the most exciting aspects of diving but does have some inherent risks and dangers that divers need to be aware of.
“Danis Wreck spec tips :
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.
Cave or wreck?
• 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.
Why should I get my Wreck spec?
• Before you enter any wreck you should obtain 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. 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 3 days training you can safely penetrate these passages and live to tell the tale.
• 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 Advanced open water course.
Standard wreck courses, often called a speciality course, offer an insight into wreck history, focus on basic mapping, kicking techniques, and line laying. These speciality courses are aimed at the 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 40m, which means that a wreck laying in 25m allows a maximum penetration of 15m. 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. ollowing 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.
• We will practice Flutter kicks and modified frog kick during dive 3
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
Hazards of 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:
1. Sand grains: the least serious, generally falling out of suspension 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 suffer very badly, with ash deposits almost a metre deep in places
5. 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!
Keep your group small
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.
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!
1. 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.
2. 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
3. The hand signals below 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.
Ending the dive for ANY reason
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.”