Nuestra Senora de Atocha (Our Lady of Atocha) was the most famous of a fleet of Spanish ships. The ship was named for the parish of Atocha in Madrid.
On 6 September 1622, the Atocha was driven by a severe hurricane onto the coral reefs near the Dry Tortugas, about 35 miles (56 kilometers) west of Key West while carrying a vast treasure from Spanish ports at Cartagena and Porto Bello in New Granada. With her hull badly damaged, the vessel quickly sank, drowning everyone on board except for three sailors and two slaves.
As the ship went down into the water at a depth of 55 feet, rescuers tried to get into the drowned hull but found that the hatches were tightly battened. The site of her loss was marked but on October, a second hurricane appeared and destroyed the wreck.
Source: Wikipedia