Josh finds treasure from the greatest score in pirate history; the most feared pirate of his time, Henry Avery stole a fortune worth more than $100 million today; Josh leaps into the frigid North Atlantic to recover Avery's riches.

Plunging hundreds of feet below ground, Josh explores Spain's treacherous La Garma cave system and finds a floor littered with human remains more than 1,000 years old; Josh's deep dive is a quest for scientific proof of Spain's legendary King Pelayo.