I have no way to verify this, but the story goes that this container ship, loaded with weapons for the Syrian rebels, inexplicably broke in half and sank, strewing the sea lanes with containers. 

If true, excellent. It's speculated that a submarine (Russian?) could have released a bubble of air underneath, which would have risen to the middle of the ship, momentarily causing a loss of buoyancy and breaking the heavily loaded ship's back.  As good an explanation as any. 

Update:This article say it is unknown what the cargo was.

Second Update: the only source claiming there were weapons on board is not really creditable. Not linking it. 

Additional possibilities to explain this mishap:

Or even this: