Never Harass these Animals, Never corner these animals, It is important to keep in mind that these sharks are nocturnal and mainly rest during the day.
Whenever diving with Grey Nurse Sharks keep an eye out for Agitated behaviour from the shark.
Gill Racking - The Gills of the Shark will flutter, opening and shutting in an over exaggerated manner.
Mouth Gapping - The Shark will slowly open and shut its mouth.
Tail Flicking - This is what these sharks will do when feeling threatened by your presence. As the Shark goes to swim off it will give a quick flick of its tail sending out a loud crack like sound, the sound will then penertrate your body with the feeling of you being hit.
Now when taking close up photos of Grey Nurse Sharks it is really important to keep bubbles to a minimum. A leaking oring with a small stream of bubbles can be the difference bettween a good photo and a poor one. ( keep your gear well maintained)
The best way to get good photos i have found is to let the sharks come to you. Grey Nurse Sharks generally swim in a gutter or do laps so to speak within an area of reef. Simply position yourself where you think that a shark will swim past and wait.
I have found that when a shark is swimming towards you that if you keep your air bubbles plus eye contact to a minimum that the shark will swim close and not show signs of agitation, but not always as ever sharks is different. Try to learn to read the Animal.