Canadian swimming phenom Summer McIntosh was unable to beat American star Katie Ledecky in the women's 800-metre freestyle at the world championships Saturday, ending her quest to win five individual gold medals in Singapore.

The United States set the world record in the 4x100 freestyle mixed relay, clocking 3 minutes, 18.48 seconds in the swim world championships.

Ledecky, trailing McIntosh at the 700-meter mark, surged ahead on the final lap, fending off a hard-charging Pallister as McIntosh faded in the closing meters. With the win, Ledecky remained undefeated in the 800-meter freestyle finals event on the world stage dating back to 2012.