"Sushi tastes amazing. A great steak is just amazing." Those are not the words you expect to hear from a leader of the vegetarian movement. But that's how Graham Hill, founder of the sustainability website TreeHugger, feels about the fleshier components of his diet. He is a self-described "weekday vegetarian," a compromise that came about after years of trying--and failing--to adhere to a strictly vegetarian diet.

The water is blue and warm, the visibility is perfect. There might be no better place in the world to learn to scuba dive than the glassy seas around Key West, at the southernmost tip of the U.S. As I gradually master my buoyancy and hover 15 feet below the surface, I can see schools of small yellow groupers beneath the dive boat giving wide berth to a blade of a barracuda.