A diver is missing in the Hawke's Bay, after becoming separated from his companion while snorkelling.

Police called in the Lowe Corporation Rescue Helicopter after the alarm was raised at Pourerere, around 2.30pm.

It's believed the pair had lost each other while swimming back to shore.

The helicopter has been unable to locate the 56-year-old Hastings man.

Local search and rescue teams will be helped by the Police National Dive Squad when conditions allow.