About eight adults and four children escaped with minor bruises and grazes after a gush of water rushed through one of the tunnels at the Castle in Cape Town on Saturday morning, paramedics said.
At about 11.45am, Metro emergency medical services (EMS) medics and doctors, ER24, Life Healthcare and other services arrived on the scene, where they were escorted by guides to the people involved, ER24 spokesman Werner Vermaak said.
"It is understood that a group of tourists were on a guided tour when a large amount of water suddenly rushed through the tunnel they were in. Most of them were swept off their feet and sustained minor injuries.
"The tour guides calmed them down and managed to assist all of the tourists to a nearby exit where they waited for emergency services."
It was understood from the guides that everyone was accounted for. At this stage, it is not clear where the water came from, Vermaak said.
It has been raining heavily in most parts of Cape Town since early on Saturday morning.