A Silver Spring couple drowned in the Potomac River late yesterday afternoon when the car in which they were sitting suddenly plunged down a boating ramp into the water at Gravelly Point north of National Airport.

The couple had been seen arguing in the car, which was parked in a recreation area at the point. Witnesses said the woman, sitting on the driver's side, had tried to get out of the car but was pulled back inside by her husband. Moments later the car lurched forward into the river.

D.C. police said they were uncertain last night whether either of the occupants purposely accelerated the car or whether it was an accident.

The victims were identified as Eric L. May Jr., a safety inspector for the Nuclear Regulatory Commission, and Annie Margaret May, 36, both of the 15000 block of Center Gate Road in Silver Spring.

A number of people in boats and cars also were at the popular area, where spectators watch airplanes land and take off. Someone in a boat radioed police for help when the car went into the water about 5:30 p.m.

Witnesses told police the car, a 1966 or 1967 Ford Mustang, plunged until only its back end was above water.

Seconds after the car hit the water, witnesses said, the woman managed to roll down the driver's window and crawl out. She apparently was dazed or lost consciousness and was unable to reach the shore. A D.C Harbor Patrol boat arrived within minutes and pulled the woman from the water.

She was taken to National Orthopaedic Hospital in Arlington where she was pronounced dead about 6:30 p.m., hospital officals said.

The woman's husband also managed to scramble from the car but he sank and his body was not recovered until after a search that lasted about a half-hour, police said.

A witness told police the couple had been sitting in the car for some time at the top of the 15-foot boat ramp and appeared to have been arguing for several minutes.

A man standing near the car with his young daughter was almost hit by the car when it suddenly lurched forward, witnesses said.

A neighbor of the May family, Joseph Dalton, said the couple had two children, Eric, 5, and Korry, 2 1/2. A grandmother has been visiting the home, he said.

"I probably knew Eric as well as anyone," Dalton said last night. "We played tennis together. We moved into the development together five years ago." He said Mrs. May was knwon as Margaret.

Dalton said he was unaware of any problems the family may have had.

The Mays lived in a neighborhood of $100,000 two-story colonial homes near the White Oak shopping center on New Hampshire Avenue.

Dalton said the family moved there from North Carolina several years ago. "I saw him Monday night at the neighborhood pool with Korry," he said. "I'm sure going to miss him."

Although Gravelly Point is in Virginia, D.C. police are investigating the deaths because the city has jurisdiction over the river.