Swimmers counted down until the clock struck 11 Thursday morning inside the South Side High School natatorium. Their lesson began promptly, to coincide with lessons around the world.
Fifty-six swimmers and instructors participated in the 30-minute swim lesson Thursday which could become the world's largest swim lesson in history.
The event began in 2010 to build awareness about the importance of teaching children to swim to prevent drowning instances. In 2011, 20,000 people in 45 states and 13 countries participated, an event recorded in the Guinness Book of World Records as the largest simultaneous swim lesson in history
On Thursday, swimmers reviewed water safety rules, practiced safely entering and exiting the pool, and performed basic floating and swimming techniques.