Given this paragraph about triathlon, who founded ironman

Context: On Wednesday, September 25, 1974, the race started. It began with a run of a 4.8 km loop, followed by biking twice around Fiesta Island for a total of 8.0 km. Entrants would then get off the bikes, take their shoes off and run into the water to swim to the mainland. That was followed by running in bare feet, then swimming again along the bay, then one last swim up to the entrance of Fiesta Island, and a final crawl up a steep dirt bank to finish. Most participants were not skilled swimmers, so Johnstone recruited his 13-year-old son to float on his surfboard and act as lifeguard. Some participants took longer than expected, and it began to get dark as they finished their swims. Shanahan recalls they pulled up a few cars and turned on the headlights so the athletes could see. Johnstone and Shanahan were surprised by the large number of entrants, mainly coming from local running clubs. Two notable entrants, Judy and John Collins, would four years later found the event which brought international attention to the new sport: the Hawaii Ironman

Answer: Ironman was founded by Judy and John Collins four years after the first known modern day triathlon on Wednesday, September 25th, 1974.