A native of South Africa, Johnston competed in the 1952 Olympics and was a three-time all-American for the University of Oklahoma. He has called Houston home since 1962 where he pioneered Masters swimming in Texas. Since 1971 he has set 124 Masters national records and 81 Masters world records. He holds 16 Masters world long distance records. Each summer he coaches the Briar Club summer leauge swim team. He and his wife travel the world promoting swimming.