I did a lot of scuba diving in my twenties and had the incredible good fortune of getting to dive a pristine wall of the North American continental shelf. As the ocean floor gave way to a chasm of unfathomable depth, I was gifted with a wall of life unlike anything I had ever seen before. Technicolor coral and fish, unusual light filtered through deep water, bubbles from my companions and me. I only got to hang suspended there for a few minutes, but that dive has provided me with a lifetime of sense memories.