This was taken on a recent hiking trip to Lake O'Hara in Yoho National Park. Lying right next to O'Hara is Mary Lake. I took this shot of Mary Lake while hiking the Yukness Ledges Alpine Route some 240 meters above the lake. What attracted me to this shot was the different shades of green and the reflections of trees in the water. I zoomed in on a portion of the lake so that the image was divided up into sections with the different groups of trees.
This lake lies beneath 2692 meter Mount Schaffer. There is a small lake nearby named Schaffer Lake. Both of these are named after an enthusiastic, female explorer of the early 1900's, Mary Schaffer. Although I can't say for sure, but I assume Mary Lake is named after her as well.