I was talking about this one just last night. The problem is, people don't actually see other player ships in their actual location - the position syncing in sailing is terrible right now. As a result, you can kind of crash into the empty air around other ships. If it looks like it'll be a narrow miss, it's definitely going to be a crash.
The area directly in front of a ship is usually its actual location.
Probably should have that mentioned somewhere in the big sailing thread or other places people visit on the forums so it's easier to get this knowledge shared. But my syncing is usually good since I hit the ships themselves and not the invisible wall