Just watched this movie & as an Australian a few things popped up as I viewed. As the couple head down under for their fateful honeymoon, the opening shot of them frolicking on the sand & sea, is the Gold Coast Queensland. This is approx 1,441 kilometers from the GBR. The following scene sees them in Sydney on a boat complete with view of the famous Sydney harbor Bridge. Tina seen holding Koala later. Sydney is even further away from the Great Barrier Reef @ just under 2,100 kilometers away.
It was not mentioned,why the couple did visit these 2 places before heading North. I guess in the whole scheme of things, it matters the least.