The engineer Stockton fired defended the design, said that if done right the fiberglass hull can hold. He also said that carbon fiber does "season". Some strands break but after that all the ones that will have broken would have. He said the cause of the implosion was most likely water seeping into the interface between the carbon fiber and titanium dome. Due to the sub being left in sub-zero temperatures in the off-season. He posits the glue cracked and lost its water-tightness.