Can't the shark just chip away at the outside?

Apparently not.

The Bait Ball confuses the predators and there is safety in numbers.

More: http://en.wikipedia.org/wiki/Bait_ball

Reddit: "If you have not seen this, it is related and amazing. It's one of these balls of fish being attacked by birds, then at 45 seconds in... BLAMO a huge whale engulfs the whole ball. Spectacular footage."

Sharks have very sensitive noses. The vast majority of their sensory input comes from there and apparently it's like getting kicked in the balls. By doing this, the shark cannot really get at the fish without getting smacked in the snout.

If you are swimming and you see a shark, punch its nose!

Thank you for the tip, Matt!

I'm going to live every week like it's Shark Week.

What happens to a Bait Ball:

TED talk:

http://www.ted.com/talks/steven_strogatz_on_sync.html