The Sea Stack that gets left-over after killing a Sea Weed has no minimap icon. This can be really troublesome since a big part of sailing is being able to look at your map to see old obstacles you have passed before and makes it really nice to be able to right your course if you might be heading into an area with obstacles. Since the sea stack left over by killing a Sea Weed has no minimap icon, it can be really hard to remember where you might have left these sea stacks and find yourself crashing into them.
1. Kill a Sea Weed
2. Notice the sea stack left over by killing the sea weed has no minimap icon.