He is shown to be a very old crab (over 100 years old since he's Krabs' grandfather and Mr. Krabs is way over 70 years old) and wears blue sailor clothes and light brown pants. He has an eyepatch over his right eye which has a large cut, and has a large gray beard.
He has a black and white shirt and a black and gold belt. He has slightly darker red skin than Mr. Krabs, which is shown to be bruised, presumably due to fighting as a pirate.
Redbeard Krabs was born to an unknown Mr. and Mrs. Krab, the former of which might have been Mr. Krabs' great grandfather. He may have been born from one of at least two children, the other of which may have been Sally.