What had struck the hull of the ship was a massive iceberg. Though the floating chunk of ice did not actually cut through the hull, it still left enough damage so that there was no way to save the ship. How did the Captain not miss the iceberg, though? He thought he had. From the surface view of the captain, the ship had cleared the obstacle. Unfortunately, underneath the water was a different situation, and the protrusion of the iceberg just below the waterline is actually what impacted the hull.