I just saw part of a "Quest for Sunken Warships" episodes, which showed the sinking of USS Oriskany off Pensacola, to create an artificial reef for ocean wildlife and recreational diving. C4 was used to open various connection pipes to allow water in. She took 37 minutes to sink. Something to think about when pondering the sinking times of ships in GWX.
http://en.wikipedia.org/wiki/USS_Ori...rtificial_reef