An investigation into an apparent shipwreck off Maryland's Eastern Shore 15 months ago ended with the indictments of 22 persons for drug smuggling in what U.S. law enforcement officials said yesterday was one of the single largest drug operations ever uncovered in the United States.

From the debris of wood splinters and old inner-tubes that washed ashore in August 1980, investigators with the federal Drug Enforcement Administration traced a path of international intrigue, starting in the hemp fields of Lebanon and leading from the docks of Annapolis and Ocean City to the streets of California and Nevada.

Investigators believe the smugglers successfully brought 35,000 pounds of hashish into the country in that single shipment through Maryland's docks, an operation of massive scale involving an Annapolis condominum, a four-acre seaside Annapolis estate, a secluded farm in Church Hill on the Eastern Shore and three other houses scattered across Maryland.

George Brosan, the special agent in charge of the DEA's Baltimore district office, said that several separate drug rings cooperated in this single shipment, which was divided into small quantities at the various locations around the state and now is believed to be netting $25 million to $50 million in individual street sales.

The first arrest in the case was made in in Florida August as an Annapolis man, one of the alleged ringleaders of the smuggling operation was attempting to leave the country. On Nov. 25, a grand jury indicted 22 other persons connected with the case, only three of whom had been arrested as of last night.

"This is not kiddie drugs here," Brosan said. "People of this ilk do not just come along every day. This was a major entrepreneurial enterprise."

The 10-page grand jury indictment provides a dramatic chronology of a clandestine multimillion drug operation. that allegedly began in January 1980, when Baxter R. Still, a 65-year-old Florida yacht dealer who has been indicted in the case, began preparing his 70-foot trawler Annette for a trans-Atlantic voyage to Europe.

Sometime in July, according to law enforcement officials, the Annette rendezvoused off the coast of Portugal with a freighter traveling from Lebanon, and the illicit cargo was transferred. The Annette then carried the 36,000 pounds of hashish to the coastal waters off Delaware and Maryland and met up with three smaller rented boats where crewmen unloaded the hashish.

In the meantime, officials said, other members of the smuggling ring had rented eight properties around Maryland that eventually would serve as unloading points, including an estate at 901 Arbutus Dr., Annapolis, and a condominium at the Mariner's Grove apartments in Annapolis.

Everything went according to plan until one of those three rented boats, Sea Flite, a 47-foot Cris Craft, developed some unscheduled engine problems. Officials believe the smugglers tried to switch the drugs, stashed in inner tubes, from the Sea Flite to one of the other boats, but lost about 1,000 pounds at sea and left behind a trail of wood and splinters that later would be discovered by some Eastern Shore fisherman.

Those indicted were mostly from California and Florida, with the exception of Peyton Lee Cromwell, 32, the Annapolis man arrested in Florida last August. Investigators linked his rented Annapolis condominium to the drug ring when they found a note with his telephone number left behind in a raft found floating off the Eastern Shore.