As other posters have said, the numbers on the charts are mean (avg.) low water. Again, things change, but my charts are usually pretty accurate. Now, for finding the holes, drops, rises, structure, they are pretty dead on. Sonar Charts (1ft) contours are so tight, when it comes to deeper spots, they pretty much give the positions away. I can tell where to set up, how to position, how the bait will move in and out and how the target predator fish are going to set up. Pretty awesome stuff that I def. credit a lot of my success on the water to.