Forgot about those. That matches the square opening, and the coal and sludge would have different sonar returns from the rest of the surrounding material. I figured it might have been something volcanic and old, with something downrange, but I wasn't paying attention to where it was.
Lacking any kind of scale reference I'll happily accept your boiler call. Though I wonder who dropped it...
The Huffington Post listed the object as about 60' across. And the Atlantic is always hungry ... take a ship torpedoed by a U-boat in either World War. If the ship went down by the bow or stern, or snapped in two, the boilers could break free and drop more or less straight down, being heavy and relatively streamlined. The rest of the ship would fall more slowly, and remains could have ended up miles away due to ocean currents, etc.
(Ballard's books on the wrecks of the Titanic and Bismark are very good guides to the behaviour of sinking wreckage, Things like the debris field between the two Titanic halves, or the "Field of Boots" near the Bismark wreck, are fascinating.)
W.
