Video captured by a bystander shows the moment 16-year-old rookie lifeguard Ryder Williams rescued a 10-year-old boy from the ocean at Seabright State Beach in Santa Cruz, California.
The child had been swept about 15 yards offshore when Williams reached him, with several beachgoers also joining the rescue. The operation lasted just over two minutes.
President Donald Trump has since invited Williams to the White House to receive a high civilian honour.
