I think the bottom line was that the wrecks were too deep to be a viable undertaking at this stage. They certainly were dumped & are there, though I think fishing nets have interferred a lot over the years?
The stuff that has been brought to the surface has been bought up by trawler nets & they have "had" to bring it to shallower water to try & recover their nets.
I had a mate who worked on trawlers off Townsville, and he said hauling up a radial engine wasn't an uncommon occurence... at one point his boat hauled up a "complete bomber wing with engines". (he not an aircraft guy?) Apparently netting .50 ammo is common also?
There is an interesting government website that talks about WWII dumped aircraft off Australia:
http://www.heritage.nsw.gov.au/docs/air ... es_nsw.pdf
I guess it'll be too late by the time we have the technology?