There's a sign in the middle of the beach, advising you to keep well away from the turtles. That's where you'll find them. The afternoon we stopped at Punalu'u there were two on the sand, still wet from the waves, glistening against the black sand and crumbled lava flows. I kept well back, and cranked my camera up to maximum zoom. Luckily I managed to avoid getting an illiterate family in shot, who had to be hauled back from the shy beasts.
I'm particularly pleased with this shot.