Might be true.
Based on the raggie sharks I've dived with the sharks actions seem natural.
Comparing the shark in the video to great white pics found through Google, I've decided it's probably a fairly young great white and probably hasn't seen very many humans in it's life.
The shark swims up to see what this strange flailing thing is and after realizing it's just a boring human it leaves.
The video should probably be renamed to "Man pisses himself in fear of random friendly shark in Sydney Harbour"