After seeing these photos, I ran into the video above. As the YouTube blurb explains:
National Geographic photographer Paul Nicklen shares the incredible story of his personal encounter with a predatory leopard seal in the frigid waters of the Antarctic. These photographs–and many more–appear in his book, Polar Obsession. Available at http://www.nationalgeographic.com/books.
Amazing stuff. I guess I never realized how big Leopard Seals actually are.
(HT to Zooillogix)