They come and they're relentless. This Go-Pro footage captures the moment a diver's cage is assaulted by a great white shark. For at least a minute, the animal bends and bites the bars of the cage.
According to the diver, "the round buoy attached to the side of the cage was bent in half" and "some of the lining of the outside blue barrier bar was bitten through as well."
Others have pointed out that sharks are curious creatures and they explore with their mouths, that this one was likely just exploring the cage without an attack mentality.
Either way, being two feet away from a single-minded super-predator must be nerve wracking. You can hear people screaming and then start laughing in a sort of jubilated relief as they remember they are protected by a cage that seems to be holding.
All told, an intense experience. I'm glad I got to watch it on video so I don't have to get in the water and experience it myself to get it.