A memorial service is scheduled for this Saturday in Fort Lauderdale, Fla., for a man who was born in Chickamauga, Ga., and starred in football at LaFayette High School before earning worldwide acclaim as a swimming coach. Jack Nelson died last Wednesday in Delray Beach, Fla., at the age of 82 from complications from Alzheimer's disease. He would have been 83 last Saturday. After shining as a 5-fo0t-4 fullback for LaFayette in 1949, he moved to Fort Lauderdale and played semi-pro football and then played for the U.S. Air Force. But he changed from football to swimming after two years and became a world record-holder in the 100- and 200-meter butterfly events, earning spots in the 1955 Pan American Games and the 1956 Olympics.