Wreck penetrations are one of the few underwater recreational activities that additional certification is needed. The overhead environment adds an additional level of risk beyond what any other dive at the same depth incurs. Before trying to dive in an overhead environment, get trained. While wreck penetration does not require large amounts of new kit, there are some additional items that are needed to ensure your safety.
If you are recently trained, then you learned the basics of using a reel when you learned how to deploy your Delayed Surface Marker Buoy (DSMB). Wreck penetration requires additional training and practice using a reel and using it in a different manner. One of the first things drilled into you during your wreck penetration training is to always use a guideline while inside of a wreck. While some ships will have a permanent line, you will need to be prepared to lay your own line and to retrieve it. You will practice using a line first on land, then outside of the ship and finally on a penetration dive.
The reel you will want for wreck diving will likely be more robust than the one you use with your DSMB. Many DSMB use finger reels do deploy. However, these can be prone to tangling which can be a hazard while you are within a wreck. A ratchet-style reel is less likely to tangle while it is being unwound. Additionally, they are much easier to retrieve and less likely to jam.
A reel used for wreck diving is similar to those used for cave diving, however, uses only about 50 and 100 meters of line. Cave reels can be much larger. Still, the principals are the same with both types of reels. Here is an interesting article on reels that has more details
If you have been on a night dive, you will find that diving inside of a wreck has many of the same concerns as doing a night dive. While recreational wreck penetration diving is limited to the light zone, having a light within the wreck is as necessary as having lights on a night dive. The rule is you most have a primary and a backup light. If your primary goes out, you will use the backup and immediately abort the dive. Some dive teams will carry an extra light so that if one dive light fails, the dive can continue.
It is generally recommended that your primary light should be a wide beam. You will find yourself in areas of different sizes and the wide beam may be necessary from you to see some of the larger portions of the inside of the ship such as a hold. Some divers believe a smaller angle is better. Inside a wreck, there is always a hazard of a silt out. Over time a thick layer of very fine silt can accumulate. A diver may inadvertently stir up the sediment creating a condition of zero visibility. The silt in the water will cause the light to be reflected back making it even harder to see. If you have driven in a heavy fog, you will know that the wider more intense high beams will make driving harder. This is similar to a silt out. The more concentrated narrow beam while diving in a silt out will penetrate further into the silt. When a silt out situation happens, the diver needs to locate the guideline and keep their light train on it and the diver should make a physical contact with the line.
Recreational divers will generally find that a dive light with average beam angle between 12 degrees to 75 degrees will work in most situations. There are models on the market that allow you to adjust the beam size while you use the light. Some manufacturers are also creating a light that has an intense center focus with the light falling out at the edges.
You should use a dive light with a lumen output of 200 or greater and 500 or greater if you are planning on the light to assist in photography.
If you are diving in warmer water and do not wear a rash guard or a wetsuit, you should if you are going to penetrate a wreck. The inside of a wreck will have many sharp edges and with the low visibility and restricted movements it is very likely at some point you will get a cut or scrape. Wearing a wetsuit will cut down on the amount of damage your skin will take. Another factor is that the inside of the wreck will not have direct sunlight and may have stagnate water. This means you could find that the inside of the wreck is colder what outside and there may be pockets of water even colder.
Gloves are another necessity within a wreck. While the same “do not touch” rule should apply inside the wreck as it does outside, this is not always possible. You may find that you need to reach out to move a line to get by. If you are following a permanent guideline, you may find that the line has become encrusted with corals or marine life. One of my dive friends swears by his 3M™ Comfort Grip Glove. While I seldom wear gloves unless I am penetrating a wreck, I too like those gloves. They give me a good grip and are durable.
You should always dive with some type of cutting tool. I always carry a pair of trauma shears when I dive. In a wreck, it is even more important to carry a cutting tool and consider a backup as well. Lines and cables can easily snag you. Having a dive knife has both its plus and negatives. Some divers will never dive without a knife strapped to their legs, however, they can be difficult to travel with and cause legal issues in some destinations. An Eezycut Trilobite makes a good backup device. Both they and trauma shears are easy to use and you are less likely to accidentally cut yourself or a diving hose.
Get Wreck Trained first
Wreck, Cavern, and cave diving are all specialties that you really do need special training. Your general diving experience does not prepare you for the additional risk of diving in an overhead environment. Get Trained.