A quick internet search reveals the Sydney Harbour Bridge air draft is 52m. Any cruise ship taller than that cannot go under. Oriana's air draft is 54.8m, the Sun class can just manage to fit under due to their squashed funnel.

As said Rhapsody of the Seas wont fit under, neither will Radiance of the Seas. Carnival Spirit wont fit under. The Costa ships to visit here will not fit under, the Celebrity ships wont fit under, the HAL's Vista class wont fit under. The old P&O Canberra did not fit under. Even the Titanic was built taller than the Sydney Harbour Bridge would allow under.

My prediction is that in 10 years time P&O Australia will not have their current fleet and that their fleet then will be too big to fit under the bridge. With only one passenger terminal east of the bridge it is inevitable that there is going to be serious cruise ship berthing problems for Sydney that will effect us. Fleet Base East will be out as there is no terminal even though the dock was designed for high intense traffic for loading supplies, transfer of personell, parking of vehicles in a one way traffic movement using both gates. There is even an overflow parking area near the medical centre main gate. The Navy will not give up their docks for cruise ships. (Although the idea of building a cruise terminal there with docking fees going directly to the Navy might appeal to them).