I thought you SH3 skippers would be interested in this. It's a composite of sound recordings from the sinking of I-52, a large Japanese submarine heading for Lorient mid-atlantic in summer '44.
1)
http://www.hnsa.org/sound/sonobuoy2/record19.htm
2)
http://www.hnsa.org/sound/sonobuoy2/record20.htm
There's also a wealth of other sounds on this page; a real historic gem.
http://www.hnsa.org/sound/
J