Our first dive was very much about familiarisation with the boat's routine, and the crew assessing our competence level.  We dived with Karl an instructor and Jo one of the DMs.  We did a circuit around the reef, hitting a maximum of 18m.  By my standards these were short dives - 31 mins on an 8L tank.  We came across a large clam as well as much of the small fish life that you get on the GBR.