In Australia all wrecks older than 75 years are totally protected. At times younger ones have been protected as well, but as far as I know, there are now none in this category.
What annoys me is that in some countries some warships are declared war graves and you cannot dive them at all. Why? You can go to France and Belgium and walk over the WWI battlefields in paddocks that contain thousands of dead Australians (and British), go to Gallipoli and walk on the beaches and hills where thousands of Australian, New Zealand and British soldiers were killed and still lie, sometimes bones still sticking up out of the ground. What is the difference with swimming through a wreck that contains bones of dead navy sailors? I do not understand this at all.