I have an MMC and I'm betting you don't.   The mate is as qualified as the Master and probably has the same licensure as well as pilotage, which is required for a large vessel in those waters.   If the Captain stands watch at all on a large vessel, it is only one watch in the day, and all the other watches are stood by Mates.   Yes, a Master is held responsible, but the point is, he didn't put the vessel on the reef and he had no responsibility to be at the conn.

Sometimes it better to remain silent rather than type and prove you don't know what you're talking about.