[Calvin Locke]

...in recent years as many as 100 pigeons have been nesting in the submarine, causing extensive corrosive damage.

Among other sources of corrosion.

Although, I'm surprised that a non battle-tested end-of-WWII era vessel is getting this type of "historic" attention.

[Chuckster]

35 years ago I worked on the restoration of the Bowfin, now a museum at Pearl Harbor. It was a very interesting and rewarding project.