Clear waters and balmy weather make June through October the best time to visit Great Barrier Reef. The main attractions here are snorkeling, diving, and swimming which causes massive crowding during these months. So seize the day and book a room in advance! The period from November to May brings heavy tropical downpours. Moreover, this time is quite dangerous both for divers and swimmers, and the reason is deadly box jellyfish roaming in cloudy water. If you are a savvy adventurer, plan your trip from April to early May.