A big problem is that charts aren't always accurate, especially in coastal waters, where the bottom can change significantly between updates. Whole islands have been known to move around over the years.

Trigger once ran aground because the captain was wearing red goggles and couldn't see the reef marked in red on the chart. By the time WWII came along charts usually weren't as as egregiously wrong as the one that kept the Bounty mutineers safe by placing Pitcairn's Island a couple hundred miles from where it actually was, but you didn't get really exact positions until satellites.

Coastal navigation is generally point to point, frequently in buoyed channels. If you know you're 100-deg north of point X and 20 deg south of point Y, you know you're
six miles to seaward of point Q. Since those points are usually lights, and lights are shut off in wartime, they can be a bit hard to spot at night.

It didn't help that, in the days before GPS, the position you plotted on your chart was often where you were 15 minutes ago, when you took the sights and started working out the position. Get clouds for several days in a row, where you can't see the stars, and you're just taking your best guess, based on speed, distance, and mean course, as to exactly where you are. That isn't always good enough.

I personally once ran a day-sailer aground on a sandbar that wasn't supposed to be there, and hadn't been a week earlier when I had a fathom of water under the keel passing over the same spot.

J.T. McDaniel