|The adventure of wreck penetration begins with proper training in the use of wreck lines and reels.|
Ever had the urge to see what lurks within your favorite shipwreck? If so, there is a lot you should know before venturing inside.
Wreck penetration, like other forays into overhead environments, looks deceptively easy. From the outside of a wreck, open passageways filled with clear water and illuminated by beams of sunlight seem perfectly safe. The problem, of course, is swimming back out. As a diver passes through closed passageways, his fin kicks stir silt from the bottom and his exhaust bubbles disturb sediments on the overhead structure. A few kicks and breaths later, he turns around to find that nice, clear passageway clouded in a dark, impenetrable silt-out.
The sudden disorientation caused by a silt-out is dangerous in any environment, but in a wreck, it's complicated many times over. To get an idea of how easy it is to get lost in a sunken vessel--even in the best of conditions--visit any floating warship museum and take the tour. Once you are well below the main deck, try to sort out the confusing maze of passageways. Now do it with your eyes closed to simulate zero visibility. Confused? Now, imagine the ship turned on its side. Add some dangling wires, unstable structures and a few collapsed passageways and you have just a taste of the confusion frequently encountered inside a wreck. Of course, we haven't added the anxiety of no-deco limits and your limited air supply.
In Over Your Head
|Shipwreck interiors look harmless from the outside, but silt, collapsing structure and confusing passageways can disorient untrained divers.|
Recreational divers are trained to react to problems by surfacing, but the wreck penetration diver must exit the wreck before he has that option. In order to find their way to safety, wreck penetration divers trail a sturdy line behind them to mark their path. If the divers lose visibility, each diver makes physical contact with the line and follows it to clear water or the exit. In many cases, the rope literally becomes a lifeline.
Wreck penetration, however, should not be attempted without proper training and practice under expert supervision. Consider this article an overview of the line-handling skills you'll learn in a basic wreck penetration class, not a license to make penetration dives.
The Reel Deal
The indispensable tool of wreck penetration is a reel with enough nylon line to mark the way to safety. Why nylon? It's sturdy and it doesn't float. The line of choice among experienced penetration divers is #36 braided nylon line. The braiding makes it resistant to abrasion, yet it's compact enough to fit several hundred feet on a small hand reel (see photo). Hand reels should be clipped off to the diver's BC with sliding bolt clips, which are less likely to become entangled in the line than marine or swinging gate clips. Each diver in a buddy team should carry a primary reel, but only one diver at a time runs line.
Towing the Line
|Indispensable and nearly indestructible--braided nylon line on a hand reel|
Laying penetration line is an art that requires good instruction and quite a bit of practice. In fact, line-handling skills are the primary focus in any advanced wreck diving training. Here are some of the basics:
Anchor the Line. The line must extend all the way to open water. Every penetration dive begins with a primary tie just outside the wreck structure. The reel diver must choose a sturdy anchor point with no sharp edges that might cut or fray the line. Tying the line to this anchor spot is easiest to accomplish when the line has a permanent loop at the end. By passing the reel around a solid anchor and through this loop, the reel diver can quickly tie a secure knot (figure 1).
No Tangles. The line must be laid so that it does not impair the diver's ability to swim through the passage. To avoid entanglement, the reel diver typically chooses one side of the passage and runs the line as low as possible on that side. This procedure allows the diver to swim into the wreck holding the reel below his body, allowing the line to spool off as he swims forward.
First In, Last Out. The reel diver is the first inside the wreck, where he scans for potential hazards and makes a second tie near the entrance/exit in case the exterior anchor point breaks. Other divers then follow the reel diver in a single-file line, keeping the line to one side and just below the chest where it can be found easily in case of a sudden loss of visibility. When using the line to navigate in low visibility, divers should wrap a hand around the line in a loose "O" shape, but should never pull themselves along the line because they run the risk of breaking it or jerking the reel out of the lead diver's hand.
Keep the Line Taut. Penetration lines work best when run in taut, straight lines. To keep the proper tension on the line, the lead diver may need to periodically loop the line around a fixed object (figure 2). He must also tie the line to the wreck at turns or obstructions where the line direction changes. In both cases, the diver running the line must weigh the benefits of tie-offs against the difficulties they will create. Every time he ties the line or changes its direction, he forces the dive team to slow its progress in order to move around the obstruction without losing contact with the guideline.
Avoid Line Traps. Line traps usually occur when a diver pulls the line around a curvature or a bend in a passageway without properly tying it off to indicate a direction change. When this happens, the trailing line can be pulled into smaller cracks, crevices or under debris piles. Divers must also tie off the line on both sides of any obstruction such as a sharp metal edge that may potentially cut the line.
Mark the Way. Finally, the line must be secured at adequate points to keep it properly positioned in the passageway. To simplify line navigation, divers will frequently lay one line the length of a main passageway. At the farthest point, the lead diver loops the reel around a secure anchor point, then loops it around the line before clipping the reel off on the side of the anchor point leading to the exit (figure 3).
To explore side passageways, the dive team follows the main line back and ties a second reel to the main line. To avoid confusion on which way to swim when returning to the main line, a directional arrow is used to indicate the way out (figure 4).
Not for the Uninitiated
Although line handling and navigation can be complicated for the uninitiated, with proper training and a little bit of experience, line handling can become almost second nature, like any other diving skill.
A good advanced wreck course will also teach you how to modify your fin strokes to prevent silting and how to maintain perfect neutral buoyancy while handling that line. Even if interior wreck exploration is not your primary goal, the skills obtained in a course of this nature will make you a better diver.