(FORTUNE Magazine) – Divers off the South Florida coast discovered a sunken Spanish galleon loaded with gold, silver, and copper that they say could be worth hundreds of millions of dollars. The find culminates a 16-year search by Treasure Salvors Inc., a Key West company that financed the venture partly through a limited partnership of about 250 investors. The investors bought units in the partnership for as little as $1,000, and at the end of each year were given shares in whatever treasure the company found. Until now, they got close to ! nothing back as Treasure Salvors pumped millions into the search and divers unsuccessfully combed the ocean floor for Nuestra Setnora de Atocha, lost in a hurricane in 1622. Now the investors will share 5% of the treasure, a portion that could be worth $20 million. Limited partnerships in treasure hunts are as spine tingling as a walk off the plank. Treasure Salvors, headed by 63-year-old Mel Fisher, first offered partnership units to the public in 1981 after some earlier investors dropped out. Poultry king Frank Perdue, 65, bailed out several years ago because, he says, ''I'm not a riverboat gambler.'' David Paul Horan, a Key West attorney who represents Treasure Salvors, says he was forced to take a small interest because it was the only way he could get paid his legal fees. ''The only person who thought anything would come from all the pain was Mel Fisher,'' says Horan. Fuhrman Nettles, a vice president with Robert A. Stanger & Co., a New Jersey limited partnership research firm, says only wealthy speculators should consider partnerships in undersea hunts. Says Nettles: ''It's like going to Atlantic City.''