Griffin O'Neal, the 21-year-old son of movie actor Ryan O'Neal, was indicted today in connection with a Memorial Day boating accident in which Gian Carlo Coppola, son of movie director Francis Ford Coppola, was killed.

An Anne Arundel County grand jury handed down the indictment, which charged Griffin O'Neal with six counts, including boat manslaughter and driving a boat recklessly. The accident occurred on the South River near here.

Gian Coppola, 23, and O'Neal, who were in Washington to work on a movie being directed by Coppola's father, were riding in a rented 14-foot speedboat that ran into a nylon tow rope connecting two powerboats. Coppola died of massive head injuries after being struck by the rope and thrown to the deck. O'Neal received a minor shoulder injury.

Maryland Department of Natural Resources marine police, who patrol state waterways, said at the time that O'Neal told them that Coppola had been driving the boat. However, witnesses subsequently told police that O'Neal had been at the wheel. The skipper of the boat being towed told reporters that the driver "was crouched behind the wheel just as if he was trying to get every ounce of speed he could out of that boat."

"The grand jury found probable cause to believe that he O'Neal was operating the boat and operating it in a reckless manner," said Gerald K. Anders, the assistant state's attorney who headed the grand jury investigation into the accident.

An autopsy found that Coppola had a blood-alcohol content of 0.15 percent. The maximum legal level to operate a boat in Maryland is 0.08 percent. Police did not test O'Neal, Anders said.

Anders said he has been unable to contact O'Neal or O'Neal's attorney to inform them of the indictment and to make arrangements for O'Neal's arraignment in Anne Arundel Circuit Court. A trial has been tentatively scheduled for late September.

Boat manslaughter, defined as causing the death of another by operating a boat in a "grossly negligent manner," is a charge that has been used only a few times in the past decade and carries a maximum sentence of five years in prison and a $1,000 fine. In addition to the manslaughter count, the grand jury indicted O'Neal on five lesser charges: one count of reckless operation of a boat, two counts of operating a boat in a manner likely to endanger persons or property and two counts of reckless and negligent operation of a boat.

Last Saturday night, there was another boating death on the South River after two motorboats collided. A passenger in one boat, Thomas S. Southwick III, 28, of Edgewater, Md., was apparently knocked from a boat and drowned, according to Capt. Frank I. Wood of the marine police.

Police, who said their investigation is continuing, have charged a man whom they identified as the driver of the other boat, Bruce William Hartz, 36, of Annapolis, with operating a boat under the influence of alcohol.