Emerald Valley has nothing to do with a valley. It's a waterway connected to the sea filled with water so turquoise that it almost looks artificial. As the water is so crystal clear, everything at the bottom (soft corals, starfish, sea urchins) is clearly visible from the edge of the waterway. You can however swim in it, just be careful not to step on something. Amazingly, Emerald Valley isn't signposted well, but it's located across the road from Guam Power Authority.