Tasman Sea

Correct!
The Tasman Sea is a Sea region of the Pacific Ocean.
Located on the East coast of Australia, the Tasman Sea is bounded by Sydney.

Welcome to Sydney, Australia!

The general area classified under Sydney is actually broken up into 38 separate governmental districts
 over an area of around 1687 square kilometers.

Question:
Your next stop is, about, a mirror image over the Equator and about 10 degrees West of Sydney.
What island country do you end up in?

Indonesia
Japan
New Zealand