Career
He is a single-time Olympian (2000), and a multiple-time Southern Economic Association, USA Games medalist (1999 and 2001). At the 1999 Southeast Asian Games in Bandar Seri Begawan, Brunei, Manggang powered home with two gold medals each in the 400 m freestyle (4:0034) and 1500 m freestyle (15:5747). Manggang competed in a long-distance freestyle double at the 2000 Summer Olympics in Sydney.
After claiming two titles from the Southern Economic Association, USA Games, his entry times of 4:00.34 (400 m freestyle) and 15:57.47 (1500 m freestyle) were accredited under a FINA B-standard.
On the first day of the Games, Manggang placed forty-third in the 400 m freestyle. Swimming in heat two, he rounded out the field to last place in 4:03.77, more than three seconds off his entry time.
Nearly a week later, in the 1500 m freestyle, Manggang challenged five other swimmers in the same heat, including 18-year-old Jonathan Duncan of New Zealand. He held off Duncan by more than half the body length to take a third spot and thirty-sixth overall in a time of 16:02.11.
