The major sunken-treasure areas are the Gulf of Mexico, the western Caribbean, and the waters off the Florida Keys, the Bahamas, Bermuda, and the Azores. They hold the hulks of Spanish treasure ships that sank while carrying riches from the New World, 1500–1820. Some of the treasure has been recovered, but gold, silver, and jewels worth millions of dollars probably still lie below the sea. Other rich waters are those near the Philippines and the Marianas; a number of Spanish ships sank here while carrying silver coins from Mexico to the Philippines to purchase Oriental luxuries.
Many other areas of the world hold valuable shipwrecks. In the Indian Ocean, for example, are a number of European trading ships that sank while sailing between Europe and the Far East. In the Mediterranean Sea are ancient and medieval vessels that were wrecked while carrying statues, vases, cannons, and other items. Among the 1,100 known shipwrecks in United States waters are some with gold cargoes.
Treasure wrecks are sometimes found accidentally by a fisherman, a sponge diver, or a lucky treasure hunter. More often, they are found as the result of a search. Professional treasure hunters may spend months in research to discover the general location of a wreck and the value of its cargo. They study such records as naval histories, insurance company records, logbooks, old newspapers, and reports of earlier salvage attempts.
Then they search in the general area of the wreck, often with instruments such as metal detectors and depth recorders. Even with these instruments sunken ships, especially those made of wood, are difficult to find. Wooden timbers may rot away, leaving only ballast stones, metal parts (cannons, anchors, hardware), and nonperishable cargo. The remains of the wreck may be covered by coral, sand, gravel, or mud.
After a wreck is found, divers may spend months in recovering its treasure. Their equipment—besides diving gear—usually includes a hydraulic blaster, which cuts away loose sand, and an air lift, which sucks water, silt, and small objects up a pipe to the surface.
In ancient and medieval times, skin divers were able to recover some valuables from wrecks. Spanish crews used diving bells to rescue several hundred million dollars' worth of riches from their sunken ships. In 1687 William Phips, an American shipping merchant, recovered treasure worth about $1,000,000 from a sunken Spanish galleon.
The development of diving suits in the 19th century and of scuba equipment in the 20th century greatly increased the extent of underwater treasure hunting. One of the richest finds was made in 1985 off the Florida coast by Treasure Salvors, Inc., a professional treasure-hunting company. After a 16-year search, the company discovered the Spanish treasure ship Nuestra Señora de Atocha, which had sunk in 1622, and recovered more than 100,000 silver coins, hundreds of gold and silver bars, and thousands of emeralds.