Another crazy honk I encountered in the Bahama's is whoever honks while approaching a stopsign get's to go first.
That is terrifying - but in Australia we have roundabouts, where the basic rule is you give way to whoever's already on the roundabout. There are two kinds of people, those who are terrified and overcautious about roundabouts and those who race to get on them.
Stateside we usually flash our lights when you find a speed trap with a policeman waiting
Same in Oz.
Hingehead, hoping to get to Australia within a year or two to snorkel and dive the reef's anything I should know about local customs.
If you're coming to the reef you'll be dealing with people who deal with tourists from all over the world, so I doubt you'll be doing anything culturally abhorrent. But that said, a smile, a hello and a thank you are all great ways to make life very pleasant.
Just don't come over in your winter (our summer is also our wet season) this time of the year is perfect.