Here's the best way to find wrecks, either charted or for which you have numbers that don't quite match up.....
First, get out your chart. Determine the average depth and the bottom composition (if it's rocky you'll be getting lots of false depth sounder "hits", sand or mud, much less, you'll want to know this later). Get a bleach bottle, length of good nylon string (cave line works well) appropriate for the depth, and a 5 lb lead scuba weight. Tie it all together wrapping the line around the bottle snugly and evenly. Do this 4 times (i.e. make 4 of these). Number each jug with magic marker.
Get to your spot as closely as you can and toss in the bottle/string/weight device (known as a "jug"). The jug will spin as the weight sinks, spooling out the line nicely. When it stops spinning it's down (assuming the line is long enough!) Take a GPS reading on it after it settles.
Settle in and relax. Now you're going to run search patterns in circles around the jug, ever widening, with about 30' greater distance between each circle (use GPS to keep a constant distance from jug).
Assign someone to watch the depth sounder. Any wreck worth diving will show up on the sounder. Use your GPS to mark all "hits". Use your extra jugs to mark hits you plan to dive on that day.
Run your pattern out to 1/4 mile. Then go back and dive your significant hits.
Collect your jugs when your done.
Tom
ps- Here's a couple of links you might find helpful
http://chartmaker.ncd.noaa.gov/hsd/hsd-3.html
http://anchor.ncd.noaa.gov/awois/search.cfm
