Docker graduated from Griswold High School in 1973 after competing in four sports. His college years were spent at Buena Vista University at Storm Lake, Iowa. He swam competitively in college and earned four letters. Docker helped the team win its conference championship four years in a row. He specialized in the 200 and 500 freestyle races.
Docker started his coaching career in 1976. In 1991 he merged his team, Team Nebraska, with OWSC and BSC to form Swim Omaha. In 1999 Docker was the head Ralston High School swimming coach.