A civilian employee of the Navy's ship research facility in Carderock who drowned Wednesday night in a testing pool there was concluding a test when he apparently slipped and fell in the water, a spokesman said yesterday.

Jerald W. Grant, 34, a naval architect who had worked at the naval Ship Research and Development Center in Montgomery County for 10 years was pronounced dead at Suburban Hospital at 11:37 p.m. Wednesday.

According to a spokesman for the facility, Grand and two colleagues were concluding a test of a ship model in one of the building's two indoor test basins when the accident occurred. The pool is 20 feet deep, about 50 feet wide and slightly more than a half mile long.

Grant apparently slipped, the spokesman said, while standing beside the basin as his two colleagues were securing the ship model. He flailed the water, according to the spokesman, shouting, "Help, help, I can't swim!"

The spokesman said the other two workers, William Harrington and Eugene West, said later they pulled Grant out and that he could not have been under water for more than two minutes. The rescue attempt included poolside efforts at mouth-to-mouth resuscitation, the spokesman said.

Grant, who lived in Catlett, Va., was married and the father of three children.