OT - Aussie Marines!

[Sanjuro]

I agree that large scale beach landings against defended positions are unlikely; however, a trained amphibious brigade is the ideal way of getting a defensive force into position, with the heavy weapons, armour and logistical support if a threat becomes apparent.
It would be theoretically possible for an invader to land a force somewhere on a remote part of Australia's coast, with the plan of expanding the beachhead before defending forces can be brought to bear- but if Oz has a unit capable of landing on the next beach, ready to fight, that invasion becomes much less practical.
Ok, setting up an amphib brigade ready to invade yourself would be unusual, but it seems (to this ignorant foreigner, anyway) a novel and effective solution to some of Australia's unique defensive problems.