Where a lone street of the seaside hamlet of Schoenmakerskop terminates on the edge of a bluff, a solitary bronze cannon aims out over the ocean and a small, secluded bay. It marks the site of an extraordinary shipwreck discovered in 1977. The cannon itself was pulled from the site and dubbed the “miracle cannon” because it remained perfectly preserved despite centuries on the sea floor. In 1647, the Sacramento, a large Portuguese galleon, was on her maiden voyage. The ship carried a massive consignment of artillery pieces meant for…