It happened at Falcon Cove, just south of Cannon Beach.
Rescue crews were able to get the man and a 7-year-old girl out of the water, but a 4-year-old boy is still missing.
A Coast Guard helicopter was deployed to search for the missing boy, but crews had to suspend the search for the night.
As for the man and the girl, Coast Guard officials said they were unresponsive at the scene. Both were taken to the hospital, where the girl later died, according to KPTV. The man is expected to survive.
A high surf warning was in effect all day, and Tillamook County Emergency Management warned waves could reach heights of 25 to 30 feet.
Those in the area were advised to be cautious of coastal conditions, including large waves and logs.
The Coast Guard urged people to stay away from jetties and rocks during dangerous surf conditions.
The Oregon State Police is in charge of the case.
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