An Oakton man was missing in the Potomac River last night after the canoe in which he and his 11-year-old son were riding capsized near Great Falls. Earlier yesterday, a 39-year-old Washington man drowned in the Potomac after falling from the river bank in Georgetown while fishing.

In a third incident, an 18-year-old Beltsville man was rescued from rocks near Great Falls after falling an estimated 35 feet while climbing. He was taken to Suburban Hospital, where he was listed in critical condition last night.

Authorities said their search for Parmely Daniels, 45, will resume at dawn today. Michael Daniels, 11, of Reston, was rescued in good condition from a rocky island in the river after the canoeing accident, which occurred as he and his father came over a spillway dam about one mile above the falls, authorities said.

The father and son were believed to have set out from River Bend Park, which is above the falls on the Virginia side of the river.

Both reportedly were wearing swim suits and neither was said to have been wearing a lifejacket when they came over the spillway dam, a section of the river where currents are often fast and strong.

"The water can be very deceiving out there--the force and swiftness of it," said Gary Mesaris, a spokesman for Fairfax County fire and rescue services. He said the canoeists had "evidently not been accustomed to the swiftness of the current."

The river in the Great Falls area is the scene of several drownings among swimmers and boaters every summer, particularly when the water is high and flowing swiftly.

After the canoe capsized, the boy was washed by the current to the rocky island about 100 yards from the spillway, where he was found by rescuers. Strong currents and the presence of debris impeded the search for Daniels yesterday, Mesaris said.

In the earlier incident, which occurred about 11:45 a.m., Alton Montgomery, listed as living at 1011 Florida Ave. NE, was fishing from the bank of the river near 30th Street NW, a few yards upstream from the Thompson Boat Center, when he slipped and fell in.

His body was recovered about nine minutes later by a D.C. police harbor unit boat. He was pronounced dead a short time later at George Washington University Hospital.

A harbor unit officer estimated last night that the river's depth ranges from 15 to 20 feet near where the victim fell in.

The 18-year-old man rescued by the Cabin John Volunteer Fire Department after the climbing accident was identified as Robert Hayes. No street address was immediately available. Rescuers said he broke his left ankle and suffered possible internal injuries, but that he did not lose consciousness.