Kwok was born in Laguna Hills, California from a Hong Kong father and an American mother, giving him distinct, blond-haired and blue-eyed features, and a dual residential status.

After South Coast Aquatics ceased operations, Kwok joined numerous small clubs until he finally settled with the Mission Viejo Nadadores under head coach Terry Stoddard.

[3] Kwok attended Laguna Hills High School, where he swam for the swimming team, and achieved senior national marks in the 200 and 400 m individual medley, and in the long-distance freestyle (400 and 1500 m).

After graduating from Laguna Hills High School in 1995, Kwok accepted an athletic scholarship to attend the University of Southern California in Los Angeles, where he played for the USC Trojans swimming and diving team under head coach Mark Schubert.

[2][4] A genuine product of a paternal heritage, Kwok retained an independent athletic status and held his family dual residency to compete internationally for Hong Kong in swimming.

[15] On that same year, at the Asian Games in Bangkok, Thailand, Kwok powered home with a well-deserved bronze medal in the 400 m freestyle, earning Hong Kong's first podium finish in swimming.