He was found by Surf Life Saving personnel, Mr Brettkelly said, and the rescue helicopter guided a rescue boat to the scene.
The swimmer was brought ashore and CPR was carried out by ambulance staff and lifeguards.
"Sadly, he died on the scene," Mr Brettkelly said.
The man was taking part in the Sand to Surf ocean swim series.
Categories in the annual swimming event range from a 200m children's race to a 2.6km event for ages 12 and over.
Mt Maunganui's lifeguard service directed enquiries to the police - who said a swimmer was reported missing earlier in the day.
"We had a report of a missing swimmer at around 11.25 [yesterday] morning. Officers arrived and the swimmer had been found on the beach with paramedics. He subsequently died," a police spokeswoman said.
"That's a matter for the coroner and the cause of his death is being investigated."
Event director of the ocean swim, Scott Rice, also confirmed the man had been part of the event.
"A person was rescued from the water in one of our swims. They brought them to the beach, first aid was performed and he was placed in an ambulance," Rice said.
"I know no more from there."
All other swimming events following the man's death were cancelled.
A witness said she saw an older male being taken up onto the beach from the water, where CPR was performed on him.
