What length of board shorts are best for surfing?

I'm going to take up surfing, and I'm shopping for the appropriate gear. Are board shorts that are slightly above the knee the only acceptable length, or are short shorts okay too?|||I surf in my bathing suit,Girls don't need board shorts...................|||Technically it would be best to surf in the nude. I don't know why board shorts would be the only acceptable style to surf in.|||Wear what ever is the most comfortable. That's probably the most important thing to do. I have a couple different pairs of board shorts and they all chafe somewhere if I surf too long (3+ hours). I even have a pair of the Hurley Phantom 100s, they are awesome and feel like your wearing absolutely nothing but then again it feels like wearing nothing when your butt cheeks are rubbing against the wax on the board also, which is not the most comfortable thing.