What kinds of ships get used for these Australian reefs, or for target practice? Destroyers, frigates, and auxiliaries for the most part, I would guess. And do you know where to find any pictures or video online of any of those sinkings?:hmm: I remember seeing footage of the sinking of the N. Korean freighter Pong Su being sunk as a target earlier this year, and have seen pictures of tugboats and fishing vessels being sunk as reefs.
Here's some various ships being sunk, as well as some obsolete tanks and personnel carriers.

(You can navigate to different sections of the page, but I've added more links for convenience).
http://www.njscuba.net/reefs/misc_materials.html
http://www.njscuba.net/reefs/chart_0...ty.html#Bushey
http://www.njscuba.net/reefs/chart_13_cape_may.html
More sites:
http://www.ships2reefs.com/displaycommon.cfm?an=6
http://www.goldenrockdive.com/cb.htm
http://www.diveexhmashobart.com/ship/scuttling.html
http://www.hmasperth.com.au/home.html
http://www.capedive.com/swan.htm#ArtificialReef
http://www.buccaneerdiving.com/wreck/sinking.htm