For something truly memorable, Sea Life Sydney Aquarium offers a private "underwater" dining experience like no other, with six stunning locations within the reef exhibit to choose from. Each comes with a stunning vista and plenty of sea life roaming, with prices ranging from $450 - $550 per couple depending on location choice.
The current available dates are November 9, 14, 16, 21 and 23. I will update when further dates released.
The experience includes a self-guided tour plus a three-course dinner and drinks, it's a very private affair - except for the company of hundreds of fish, turtles, sharks and sawfish cruising the reef.