[ar10]

Yes, but once you get a crack in the cement and the saltwater gets to the steel inside you get rust jacking or spalling and then it only a matter of time until it all fall apart

[az_gila]

There are (or at least were few years ago) 10 concrete ship hulks forming a breakwater for a paper mill in Powell River, BC.

My picture of the entire breakwater -

My picture of the ex-navy ship Quartz which was nuked as part of the Bikini Atoll tests.

http://www.navsource.org/archives/09/46/46150.htm

[chb]

That is certainly a case for some form of sealant on the steel. By the way, I did not say or mean to imply that I was one of the enthusiasts.