Variously named the English sole or the Lemon sole, I've seen these guys many times diving on shallow, sandy bottoms. They have pretty good camoflage, and I've startled a few cruising over them. Sometimes they're covered with a thin layer of sand, and are invisible until they decide to pick up and move.
This picture, as indicated, is copyright Owen Lloyd; I got it from his website, detailing some of the dives he's made. I like his site because he's been diving (and photographing) at some of the same places I have.