A man died while leaping off rocks into the Swan River.

The man dived into the river at Blackwall Reach, a popular but dangerous cliff-jumping location in Bicton, about 4pm Sunday.

Onlookers said he was unconscious when he surfaced.

Other swimmers dragged the man to rocks at the bottom of the cliff and desperately tried to resuscitate him.

Water Police officers were called and used a boat to take the man to shore where he was met by an ambulance.

The man was taken to Fiona Stanley Hospital, but was declared dead.

The man, believed to be in his 30s, was one of scores of people who were jumping from the cliff on a hot summer day.

Even after the incident, people continued to leap from the cliff, which is about 10m high.

The water at Blackwall Reach is 25m deep in parts.