I haven't played a lot of naval so this may not be a new thing, but in a recent GW game I was thwarted by invisible walls in the water. I suspect this may have been caused by water depth, but there was no way to see this visually except that I noticed metal spots apparently very shallow in the water. In the screenshots, the lines show inexplicably impassable bits of ocean, and the red circle shows the metal spot that looked very shallow.
