The Telam state news agency says the lightning bolt struck Thursday afternoon in Villa Gesell, a town 320 kilometers (200 miles) east of the capital of Buenos Aires.
The 16 adults and six children injured were taken to a local hospital. Officials say two women suffered serious injuries.
Argentina's National Weather Service says the lightning was caused by a sudden storm with "a great movement of ascending air and water and lots of electrical activity."
Take ABC13 with you!
Download our free apps for iPhone, iPad, and Android devices