Kim became the first ever South Korean swimmer to train in the United States, where he attended the University of Florida on a full athletic scholarship.

[3] While swimming for the Gators, he received five All-American honors, and placed fourth in the 400 m individual medley at the Southeastern Conference (SEC) championships, with the school's sixth-fastest all-time record of 3:51.90.

In 1999, Kim entered his junior season for the Florida Gators, when he placed eighth in the same program at the U.S. Open in San Antonio, Texas, touching the wall in 4:30.19.

[8] When his nation hosted the 2002 Asian Games in Busan, Kim won only a bronze medal, as a member of the South Korean team, in the 4×200 m freestyle relay (7:29.36).

Swimming in heat two, he set a South Korean record of 4:23.05 to claim a second spot by a 4.50-second margin behind winner Dean Kent of New Zealand.

[15][16] In the 200 m individual medley, Kim participated in heat three against seven other swimmers, including fellow three-time Olympian Jacob Carstensen of Denmark.

Kim held a South Korean record (4:23.05) in the 400 m individual medley from his third Olympics in 2004, until it was broken by Han Kyu-Chul at the Asian Games two years later (4:21.75).