Long Beach Police Chief Flint Wright says the girl's body washed ashore Saturday morning. He identified her as Lindsey Mustread.
The girl and her 9-year-old brother had been wading in the surf on the Long Beach Peninsula on Thursday when they apparently got caught in a rip tide.
Her brother, Kenneth, was rescued that afternoon after treading water for about a half hour. A Coast Guard air and water search for the girl for seven hours Thursday.
Wright has said the family is from Chimacum on Washington's Olympic Peninsula.