This problem is exactly why I didn't put GPS numbers in my Chesapeake Guide, and hesitated to put them into the Mid Atlantic Guide then spent a lot of time explaining that when you plug those numbers in, you won't end up exactly ontop of a wreck. Different datums is usually the biggest problem, but even when you plug the same numbers into two units set to the same datum, you can't expect to get dead-nuts-on. I tell readers that when they use the numbers in Rudow's Mid Atlantic Guide (which are all verified GPS coordinates) they need to plan to go to the spot, mark it on their unit, then run a circular search pattern to find the structure, wreck, or whatever. You'll be in the right neighborhood, and 1/2 hr or so of searching should do the trick (large items, like the Hot Dog, are big enough that it won't take any time at all, but small wrecks and the like are tougher.) If you're gathering varying numbers for the same wreck from web sites & such, plot them on a chart, then plot a spot in the middle of the cluster of marks and start your search there. You shouldn't be more than 1/4 or 1/2 mile off (or some of those numbers may in fact be "bad.") Good luck!