He improved his best time by more than two seconds in 1988 and broke the world record .
Dave Berkoff excerpt and authors note : Dave Berkoff changed backstroke as we know it , extended underwater dolphin kick to more than 30 meters on his start .
Dave Berkoff improved Dave Berkoff 's best time by more than two seconds in 1988 and broke the world record .
Dave Berkoff excerpt and authors note : Dave Berkoff changed backstroke as we know it , extended underwater dolphin kick to more than 30 meters on his start .