

Two words: Fran Crippen.
In USA Swimming, changes were made for the well-being of the athletes. Organizers of an open water swim in Fort Myers have reconsidered the timing of their race because it may exceed the recommended water temperature of 87.8 °F (31.0 °C), or the combined air and water temperature of 145.4 °F (63.0 °C).[8]
United States Masters Swimming (USMS) adopted a warm water conditions rule to the USMS Open Water Rule 302.2.2 (3) A swim of 5 kilometers or greater shall not begin if the water temperature exceeds 85°F (29.45°C). A swim of less than 5 kilometers shall not begin if the water temperature exceeds 87.8°F (31°C