Robot sub finds ‘Holy Grail of shipwrecks’

Spanish treasure fleets that traversed the Atlantic Ocean to the Americas and back were a 16th century invention as important as free two-day shipping. Organized 70 years after Columbus’ first voyage, the fleet was made up of several specialized ships with one primary goal: Exploiting the riches of the New World as efficiently as possible.

The San Jose, the largest galleon and the flagship of one group of Spanish ships that started sailing in the 16th century, was big and — thanks to 62 bronze cannons engraved with dolphins — deadly enough to deter or destroy ships, whether pirates or rival nations.

Except when it didn’t. On June 8, 1708, during the War of the Spanish Succession, the San Jose’s gunpowder ignited during a battle with British ships, sending 600 doomed sailors to the bottom of the Atlantic Ocean — along with gold, silver and emeralds from mines in Peru, a total haul valued at some $17 billion in today’s dollars.

It stands as one of the most expensive maritime losses in history. And “the Holy Grail of shipwrecks” stayed underwater, undiscovered for more than 300 years.

Enter a tiny submersible robot named Remus 6000 — packed with sensors and cameras and capable of diving 4 miles underwater — that has discovered the centuries-old final resting place of the sunken ship.

The unmanned underwater vehicle, operated by Woods Hole Oceanographic Institution, uses far-reaching sonar to identify objects on the seafloor — then circles back to take pictures of anything worthy of a closer look.

Remus 6000 has used the same tactic to find the remains of Air France 447, two years after it crashed off the coast of Brazil in 2009.

The wreckage of the San Jose was discovered two years ago, but the location off the Colombian port town of Cartagena and other details have been closely-held secrets.