Commanders can be Captains of many vessels and are referred to as Captain.
To: haffast
“Isn’t the officer in charge of a ship ALWAYS called the Captain, regardless of his rank?”..
Ding, Ding, Ding!!!!! We have a winner. Indeed a “Captain” of a U.S. Navel vessel can be any rank of commissioned officer such as Ensign, LTJG, Lt., LT. Commander, etc..