I will believe that no damage has been done when I see underwater videos. As far as marine life goes, 200 feet is not really "void of life".
"They did not explode", "They are small so it is fine", "There is way worse happening" are bad excuses for dumping anything on an endangered location. I do hope they manage to salvage them, because nobody has any idea how the metals will react to a long exposure to salt water, currents, pressure etc.
ps: obviously nothing in comparison to the poison-covered hulls of the coal carrying boats... but still... when I see a big pile of dump in the wild I do not throw crap at it telling "yeah it's not my little crap that will do much compared to what is already done".