Let's face it, before Jaws gave sharks in general a bad name, they already had a bad name as man eaters. Since the first person dipped their toes in the ocean, sharks have honed in on man's scent, sensing a tasty lunch. That, or the shark has incorrectly identified a dude on a surf board as a seal. A sweet, juicy seal.
Here's some pictures of the after affects of a shark that had a foot fetish:
While we all real know that fish are friends (not food) but tell that to polar beers. They seem to have a thing for human feet too...
This picture was the result of a polar beer attack on an Eskimo