A 46 year old hull facing constant and repeated flexing when it hits a well timed wave that causes the two outermost points of the ship to ride high and the middle to be unsupported.
It’s not something I would expect but it’s amazing what slow moving strong forces can do to metal.
Early Liberty ships suffered hull and deck cracks, and a few were lost due to such structural defects. During World War II there were nearly 1,500 instances of significant brittle fractures. Twelve ships, including three of the 2,710 Liberties built, broke in half without warning, including SS John P. Gaines, which sank on 24 November 1943 with the loss of 10 lives.Metallurgists learned then about the ductile to brittle transition of steel when it gets cold. That obviously isn’t the case here. Maybe this hull exceeded its fatigue limit, which initiated a brittle crack.