Michele Mitchell and China's Li Koncheng successfully defended their platform titles in the McDonald's Invitational in Fort Lauderdale, Fla. Greg Louganis placed fifth behind Li in the men's competition after he hit the platform with his feet during a dive.

Louganis, who had not lost a platform event since the U.S. Indoor Championships in April 1984, blew his sixth dive at the International Hall of Fame pool. On an attempted 1 1/2 somersault with 3 1/2 twists, the bottoms of both his feet hit the platform and he ended up hitting the water on his side.

Louganis wasn't injured, but his chances of winning the 10-dive final evaporated as the judges gave him one score of 1.5, one of 0.5 and the rest zeros.

Li scored 635.22 points, to 619.23 for runner-up Andrei Kvochensky of the Soviet Union. Georgy Chogovadze, U.S.S.R., was third at 614.19, Don Watson, U.S., fourth at 601.68 and Louganis fifth at 574.86.

Mitchell held off Anzhela Stasulevich of the Soviet Union by the slimmest of margins, 654.77 to 654.47. Chen Lin and Lu Wei of China were third and fourth.