Aaarrrh!

I'm wondering about the accent used by Hopkins (who is amazing in this). E.g. Instead of Sir he says saarrh. It sounds brilliant and really adds to the character. It is quite well known trivia that the accent we associate with pirates is pretty much down to one of the first pirate movies and that the actor decided to put on a south West England accent. So I wonder if Hopkins added that to fit with the theme or if it was accurate for the real life Bligh.