Most of the Diver Guide books are rough enough for co-ordinates. I like to fly around the wreck a few times in the rib using the sounder to really map the wreck clearly and set the gps to "show trails" you can hit the WPT button a few times on really interesting looking bits as you start going around more slowly and gradually build up a few WPT marks to get the best estimate for dropping a shot on it. I find with a decent sounder even well broken wrecks show ok if you can read them properly, not a hard game really with a bit of practice.
