Orinally a poem post Civil War that makes a metaphor comparing Lincoln to a captian of a boat who dies at the end, the phrase became famous from the 1989 movie "The Dead Poet Society" staring Robin Williams. The whole point of the phrase is that William's character was an English teacher who had his student's address him with that phrase while standing on their desks.
Someone who states something that is extremely obvious to the rest of us.
A person who is a little slower than the rest of us only to bring something to our attention way after it already happens.
A dude who bring girls on his boat, then fucks them, then makes the walkthe plank! It's a fucking GREAT website because it has a mixture of porn and disrespect!