Down Under Dive is one of several companies in Cairns that offer scuba dive courses. These dive courses include several dives on the reef and upon completion give you PADI certification, which is essential for diving on the reef.
Like other dive schools in Cairns, Down Under Dive has several different courses but the open water courses are the most popular; these courses combine theory and pool dives with a couple of dives on the Great Barrier Reef. Open water PADI courses generally run over four to five days, the cheaper courses involve daily trips out to the reef and the more expensive course include accommodation aboard a boat on the reef.
You can still dive without PADI certification, but this will involve doing an introductory dive as part of a day trip to the reef. An introductory dive is a good way to find out whether diving is for you.