It's interesting how our concept of the environment, and what is an acceptable way to treat it, has changed so much over the years.  One would think that a better way to go would have been to scrap and recycle the steel in them, but simply put, it was probably cheaper and easier just to dump them, with government approval.  Perhaps it had something to do with claiming the loss to insurance?  Lost at sea?  Dunno.

I think it's been mentioned before on here, but in 1969 Volvo dumped 26+ partially assembled Volvos in the Bedford Basin (Halifax harbour) due to damage at sea as well.  Here's the story:

https://atlantic.ctvnews.ca/video?clipId=1650951