What is the difference between a domestic cruise and a international cruise?

A Domestic Cruise is where you may have a stop at a domestic port of call within Australia or New Zealand or sail within Australian or New Zealand waters (when our ships sail out of New Zealand), government issued ID such as a drivers licence will be accepted as proof of ID to board and minimum age to travel is 6mths.
A International Cruise is where your cruise will visit a foreign port, a passport is required (same as if you were to fly to an international destination) and the minimum age to travel is 12mths.