While the Caribbean has hurricanes, the
South Pacific has cyclones, identical phenomena,
with seasons six months apart. This year
Queensland had three cyclones in five weeks,
two labeled category five.
The Nimrod Explorer did not have any trip
  cancellations due to the cyclones, a representative
  told us, though one itinerary was cut short
  by two days.  
Despite a “swag of rain,” Mike Ball of Mike
  Ball Dive Expeditions said that Cairns missed
  the brunt of the cyclones and, “Cairns operators
  anticipate periods of less favorable weather in
  the Dec to Apr season.” Historically his operation
  loses a week of diving every 2-3 years in this
  period, but this year has not lost a day due to
  weather.  
However, 200 miles south of Cairns in
  Townsville, Tropical Cruise and Dive lost nearly
  a week of diving in March due to Cyclone Larry,
  says owner John Magrin.  
The Australian government estimates that
  only one percent of the Great Barrier Reef
  had severe coral damage. The dive shops we
  contacted claim little if any damage.  
Nonetheless, if you have Australia in your
  plans, consider the season.