It was produced by the collapse (implosion) of the ARA SAN JUAN pressure-hull at a depth of 1275-feet.
Is that a determined fact....or an assumption based upon the Design Crush Depth for the Boat?
I am still trying to absorb the fact that something serious enough...and sudden enough to prevent the Crew from blowing all tanks using compressed air....and thus take the Boat to the surface....no matter how rough the seas and uncomfortable the ride would be....just what could it have been?
My first guess would be a Hydrogen Gas explosion.
Some of you scoff at surfacing being a valid option.....I very much differ.
If you get enough seawater into a battery compartment to short out the batteries....you would have to fear that it could get into contact with the Battery Acid and that would produce both Hydrogen and Toxic Gases.
Ventilating the Boat becomes the primary preventative measure and that could only be done on the surface.