When photographer Paul Nicklen, diving under the ice in Antarctica, approached a leopard seal, at first it threatened him, but soon relaxed and brought him... a dead penguin for him to eat.
See his stunning, amazing photos here.
Leopard seals are huge, and have a reputation of being dangerous to people, as well as penguins--their main prey. A few years ago, a woman diver in Antarctica was killed by a leopard seal.
It's hard to know what to make of Paul's encounter with the seal. I've sat on beaches in the Galapagos, looking into the eyes of young seal pups, imagining I'm communing with them. It's a wonderful feeling when you imagine you're communicating with a wild animal. Probably it's an illusion most of the time.
Like the penguins, Antarctic seals have no fear of humans, because until about a century ago, there were no people in Antarctica. In the absence of fear, it's possible for a mammal, and even some birds, to show curiosity towards humans. I've had penguins walk up to me, when I'm standing still, and pick at my pants with their bill.
Some animals raised by people will show this kind of playful behavior--but the chances the seal was raised by humans are about zero.
If some basic behavior has been frustrated, many animals will behave abnormally. For example, the leopard seal in question was female. If she had recently lost her pup (offspring), she might be highly motivated to shower maternal affection on some other creature. Interestingly, Paul was about the right size for a young seal.
That's my best guess, but we'll never know.