Two young men who had been fishing on an island in the Potomac River when they responded to the shouts of nine persons stranded nearby on a raft apparently drowned yesterday in the swiftly flowing current, authorities said.

The nine persons who had been wedged in their rubber raft against the base of a small dam about one mile north of the Chain Bridge were later towed to safety by a Park Police helicopter.

A search in the river yesterday for the bodies of the would-be rescuers was unsuccessful. By late last night neither body had been recovered. Police declined to release the men's names until the bodies were found.

Those on the raft had set out from Cabin John, intending to make a leisurely downstream journey towards the District of Columbia.

The river into which they pushed their raft was not the same as the placid watercourse on which several of them had made a pleasant downstream journey last fall.

Brown, colored and swollen by the runoff from recent rain and thunderstorms, the Potomac flowed fast and high yesterday.

Within a short time their raft was jammed against the base of the dam. Water gushed all around them.

"We could not get out," said Cliff Beasley, 38, of Alexandria, one of the rafting party.

"It was like being in a box," he added, 'with concrete on either side."

About two hours into their cold, wet ordeal those on the raft saw the two men fishing on Snake Island, about 40 yards away.

"We yelled, 'hey, get help for us!'" Beasley said. He said the young men, neither wearing a life-vest got into their own boat, a 10-foot flatboat.

"Then," Beasley went on, "we couldn't see anybody."

Someone on shore told Park Police that the swift current had pushed the boat with the two men into another dam nearby.

The boat was later recovered.

About 1 p.m. a Park Police helicopter dropped a rope to the seven men and two women on the raft, and towed them about 50 feet to shore.

"We stayed in the raft," Beasley said. "No one could possibly swim in that water."