Police in Oregon say a father was holding his two children, ages 7 and 4 when they were swept into the ocean near Cannon Beach on Saturday.
The coast guard suspended its search for the 4-year-old boy. Officials say a 7-year-old girl was found and was later pronounced dead at a local hospital.
The children's father was taken to the hospital, but his condition is unknown.
People flocked to beaches over the weekend to see the so-called king tides, which only happen a few times a year.
The National Weather Service says waves reached as high as 30 feet in some areas.
Officials are urging people to stay away from jetties and rocks during the high tides.