Most shark attacks do indeed take place in less than 6 feet of water. It's not what it appears though. Think about it. At what depth is the largest concentration of people in water that sharks inhabit? At the beach, most people won't go out in the water when it's over their head. Most people are under 6.5 feet tall, so it makes sense that they will stay in water 6 feet and under. I think the majority of shark attacks occur in less than 6 feet of water due to the concentration of people and the noise level that attracts sharks.