Yes many times in various places around the South Pacific but mostly on the Great Barrier Reef in North Queensland Australia where I did my diving certifications and did some voluntary work with the local University helping to reduce the numbers of the Crown of Thorns starfish which was decimating parts of the coral reef back in the 90's. I also had a volunteer job taking tourists - mostly Japanese for guided dive tours of the reef. I particularly enjoyed diving on ship wrecks and my favourite dive woukd have been a dive in shallow waters near Guadalcanal which was the site of a fierce US Marine landing during WW2 and in this picturesque lagoon was many landing craft some still with jeeps inside, rounds of ammunition, weapons etc.