I am perplexed after reading wreck diver training outlines and talking to a couple of instructors. IMHO, treatment of silt-outs is incomplete and backwards. I am a firm believer that divers need to spend a fair amount of time in zero visibility before they penetrate a wreck or even start a wreck diving class.
Here's the logic:
Wreck divers will eventually find themselves in black-out conditions. It really doesn't matter why. All your lights can fail. Silt can be stirred up by an awkward move, another diver, shifting debris, or wresting a prize binnacle to sunlight. In the end you are in the dark and have to deal with it.
Everyone's first experience in black water is uncomfortable at best. Symptoms range from a little paranoia to "get me the hell out of here" panic. Air consumption goes up, time perception is shot, and you reflexively recoil from the slightest touch -- making matters worse. Almost everyone gets over it in time.
IMHO, the great majority of wreck diving classes compound the problem. They place great emphasize on avoiding black-out conditions and address managing it with lip service. All the talk about avoidance, spare lights, and depending on your buddy isn't very useful when you are suddenly alone and in the dark. That dread and total lack of habituation is a recipe for disaster.
How are you going to monitor your air supply if you can't see? How are you going to find your buddy -- who might be in full panic mode? How are you going to get out if you can't think straight? Becoming comfortable in these conditions far in advance of being faced with them can turn a deadly situation into an inconvenience.
OK, so how do I learn?
You don't need an instructor for this. You have no idea how long it will take; it is almost entirely mental preparation. You need to feel alone. Have a buddy on the surface watching your bubbles if you feel it necessary. You don't need to be in more than 5-8' (1500-2400mm) of water.
Find some shallow ink-black water in a safe location to practice in. Try to perceive as much as possible from your other senses -- but wear gloves. It is best to find a mud bottom and stir it up if necessary. If that is too difficult, start by blacking out your mask with tape or turning your light off on night dives, but remember that is isn't quite the same. I have no idea why. Make sure you graduate to black water during the day. You will be amazed what you can learn in water shallow enough to stand up in.
I was lucky. One of my six days of ocean dives in Scuba school was devoted to black water. The instructor would tie a large nut onto a ping pong ball with about 3' (1 M) of string. Then he distributed about 30 of them in really shallow water with a mud bottom and zippo vis. Competition between students to recover the most ping pong balls earned them two air fills and coveted bragging rights. The desire to win and not look like a wimp probably helped this all-male class. I didn't appreciate it at the time, but those dives made my first night dive really easy along with US Navy Diving School years later.
When is it enough?
You will know. Air consumption will be at or near normal, you won't flinch every time something touches you, and you can start to "see" with your hands. Then you are ready to start your wreck class.
