The Rules of the Road / COLREGs test that you have to get a 90%+ on, same as the USN bridge officers. I called it the Coast Guard test, but that was a bad way of putting it(was sans-caffeine at the time, apologies).
The theory, in practice, doesn’t work very well. It sounds like non-professional watch-stander leading non-professional watch-standers, thus the accidents and mishaps.
The watch standers under them are, for the most part, professional. The issue you run into is that the actual OOD is probably not a professional ship driver, as someone else pointed out above. They come onboard as ensigns, get their Conning Officer qual while also doing the engineering stuff + admin etc(though admin is the bane of all mariners everywhere, I believe), and then are expected to move up from Conn to JOOD or Junior Officer of the Deck, which is generally an officer who is working on their OOD but hasn’t proven themselves yet. Once the CO buys off on them being able to stand the watch, they get their OOD qual, and are now the lead officer on a bridge watchteam. They do that for a tour or two(generally speaking they’d be an OOD for ~4ish years, the back half of their first tour and most of their second tour). After that, they either get out of the Navy or move up to department head and start standing Combat watches instead of bridge watches.
There is such thing as “information overload” and “instrument overreliance”, not to mention “paperwork overload” in the case of merchant ships.
Very true, though the Navy tends to be rather pro-active on visual scanning, having extra lookouts on the bridge as well as a lookout aft at all times underway. I have seen situations where someone gets focused in on one sensor or the other, but hopefully someone else on the watch team keeps awareness elsewhere. Obviously, this has failed recently on at least two ships.