The wave was in a protected cove. The swell was moving very slowly toward the beach, and there was no curl line, pocket, or surface tension.
George caught this wave further up the point, and double-clutched the take off...meaning he didn't drop straight in, but started out across the top of the wave face, then dropped in after he had gained some speed, but not all the way to the bottom. He reset his lateral line halfway down the face, let the mat run "flat," broke loose into third gear, dropped down to the base when the wave stood up a bit, pulled it off the bottom, and tore across the top of the wave. The track you see is left over from his bottom turn. It's a ruler straight line. It looks like a sailboard track. That's how fast he was going.
I showed this picture to the photo editor of a surf magazine back in the late 80's, and explained why I liked it. He broke out laughing.
(This video has a number of shots of George propelling himself into waves.)