The Aussies have a boat that is virtually undetectable. It is advanced electric technology, but I don't remember much else but they came up in the middle of a group of ships totally unexpected in a joint mission exercise. Very embarassing.
We should be using theirs for spy junk.
DK
Hmm,the Aussie boats(Collins class) you are referring to are infact Swedish designed subs which were built under license in Australia.There are numerous boats which are as quiet if not more quiet than those subs including the ultra modern German Type-212/214 class,the French Scorpene(both of which use Air independent propulsion) & even the Russian Kilos.
PS-it is a known fact the D/E boats are more quieter than nuclear boats when submerged-albeit for the smaller periods that their batteries can run.That will change as more and more nations adopt AIP systems -for eg,the German Type-212 can stay under for well over 20 days at a stretch.