A pod of sperm whales has been found dead after becoming stranded in shallow water on a South Australia beach.

The animals were seen swimming in the area by local people according to reports, but six whales were discovered dead on Monday morning.

A seventh whale was later seen several kilometres from the rest of the pod, local TV reported.

"You love to come and watch them swimming but when you see them like this, it's terrible," said one woman visiting the beach.