I was on a Collins class submarine in Sydney, the maritime museum has one on display.
Dave Scott

To clarify, you were not on a Collins class submarine, instead you were on it’s predecessor, an Oberon class submarine. Specifically, you were on the HMAS Onslow, a fine boat that was built back in 1967, currently a museum piece at the Australian National Maritime Museum in Sydney.

The Collins have a bit more creature comfort than the Oberons, but are still not fun places to be.