In my area, many times wreck symbols have been left on charts for historical purposes and not necessarily to indicate an obstruction to navigation - which is the main purpose for AWOIS. I'm not sure what exact parameters are used to mark a navigational obstruction, but I do know of a few wooden wrecks that only poke out of the sand about a foot in 15' of water that are not classified as an obstruction. In other words, if there's not an obstruction listed in AWOIS for a location, it doesn't necessarily mean that a wreck isn't there.
It's weird because sometimes even the AWOIS entry for a wreck may say that a search was conducted but nothing was found. I've personally found this to be untrue on many sites, although a few of them could certainly be due to the shifting of sands and silt on the bottom.
Another thing about AWOIS that you may want to take note of; I've found that several AWOIS entries in my area that denote "concrete rubble" were actually ballast piles from sailing ships with at least one of them being an actual wreck site. I suspect that some of the survey divers may not be very experienced when it comes to identify the types of obstructions or visibility underwater may play a role as well. In other words, if you have a gut feeling a wreck may be in a particular location, it may be worthwhile to check all of the nearby AWOIS obstructions.
My two cents.
Pcola
