Wreck Diving - Basic Diving Techniques
As a wreck diver there are many different techniques that you must consider. An attempt will be made here to bring out what would be considered basic wreck diving techniques. They could be divided in the following sections. Keep in mind that what is written here is just the basics and a highlight of these techniques. I would, however, encourage you to seek out a PADI Wreck Dive instructor.
NAVIGATION AND EVALUATION
Follow the wrecks layout
Use the wrecks natural lines to navigate, ie swim along the hull or along one side. Go up one side and back the other. If the wreck is fragmented, pick some prominent points and swim in a relative track. On occasion, look back to see what the return trip will look like. This is important unless you plan to do a circular swim.
Establish a baseline for widely scattered wrecks
Use a compass heading and swim in that direction, being careful to note that some compasses may not work if close to the metal hull of the ship. In low visibly or current, use your wreck reel tied off to a point as a return line to your starting point. In other words, tie off one end to the descent line and use your wreck reel as a sort of “bread dropping” technique.
Evaluate the wreck for possible hazards and stability
How is the wreck sitting ? Does it look stable ? Look for sharp objects and entanglements. Check to see if walls and structures appear strong and intact. If considering to penetrate this wreck, check for possible entry ways that are free from hazards. Your first dive on the wreck should be an evaluation dive. Period. No penetration on this dive.
Be a trained PADI Deep Diver.
This is very important. And should not be over looked. Just having the Advanced card is not enough here.
Have proper deep diving equipment available
Hang a tank at 15 feet to assure ample air for a safety stop. Set a reference line for orientation for descents and ascents. Have a first aid kit available.
Take the effect of nitrogen narcosis into account
Plan the dive to keep objectives at or above 100 feet. Remember that Nitrogen Narcosis starts to occur below 100 feet. Avoid changing your dive plan on deep wreck dives. Plan your dive and dive your plan. If you see something that interest you, plan a second dive to include that. Stay close to your ascent point so if you need to come up you know where it is. Very important if you are diving deep. Remember also that your “bottom time” on deep dives is limited.
Use a large slate to draw more accurate details.
Note distances, angle, directions, depths, points of interest. Try to make true to scale. The more accurate the better. You do this so if you wanted to make another dive on this wreck, you have a good idea how to plan other dives.
Use a compass, and other navigational aids to determine angles between prominent points of the wreck. Use your buddy to help you with this. Yes, you need to dive with a buddy. Not an option on wreck dives.
Use kick cycles and arm spans to estimate size and distance. For more accurate measurements, use a marked rope or measuring tape.
Have all necessary equipment
Have at least 2 dive lights per diver--to make sure no one will be without a light inside the wreck. Have a wreck reel and line to provide penetration line marking your way in and out. A slate comes in handy to make interior map as you navigate around. A pony is needed in case of an out of air situation. Practice using your wreck reel on the surface before you do your first wreck penetration. This is very helpful and extremely important.
Observe the limits established for diving in overhead environments.
Stay within the natural light zone -- you always have a guide to the outside should your dive lights fail. Limit your penetration to the linear distance of 100 feet. Follow the "Rule of Thirds". Use no more than 1/3 of your air descending and entering the wreck, 1/3 for exiting, and 1/3 for reserve. Remember you can always plan a second dive. On some wrecks it is very hard to see everything.
Before entering the wreck, attach the end of the line to a sturdy piece of the wreck
Put the line through a hole and tie using a secure knot. Consider creating a loop in the line and pass the entire reel through it.
After entering, secure the line to another point just inside the wreck
Check the entry for possible hazards. Look to the ceiling and see if your air bubbles are causing too much silt to “rain” down. If this happens, abort the penetration.
Move slowly through the wreck while maintaining neutral buoyancy
Keep light tension on the line as you move through the wreck. Wrap the line around non-sharp objects every so many feet. Use gentle sculling kicks to avoid silting up the bottom. When practical, pull yourself along the wreck - do not pull on the penetration line. This technique will reduce the amount of silt created.
Use the penetration line as a guide
Swim along with the line just below your chest level, and to one side. Stay close to line to reach out and grasp if at any time. Gently make and "O" around the line with your thumb and fingers.
If problem occurs - Stop, Breathe, Think, and Act. If you planned your dive correctly for air consumption, you have time to sort things out.
Stop all activity, and wait a few minutes to see if it calms some. If continues, immediately make loose contact with penetration line. If it does not settle, signal "up" and abort the dive and turn to exit. DO NOT LET GO of the penetration line. Leave the reel in place at the wreck as you exit- you can retrieve it later, unless you know all divers have exited the wreck.
Lost or cut penetration line
If you can not find the line, or it got cut, stop and look for the natural light from the exit. If necessary, cover your light to help you see (DO NOT TURN IT OFF), and let your eyes adjust. Follow natural light to exit, using the map you made along the way as a guide.
Go to your backup light. If this is your only back up, you should abort the dive and exit the wreck. Do not dive with only one working light. This is also true when diving with your buddy. If either of you have a light out problem, the entire dive is aborted.
Air supply loss
If air is low, switch to your pony bottle, and exit the wreck immediately. If you have no pony, secure your buddy's alternate air source and exit the wreck with the donor leading. Again, leave your wreck reel and line in the wreck and come back for it on another dive.