Maritime NZ won't reveal details of how the $37 million Rena clean-up bill has been spent.

A man and his 7-year-old son are missing after their dinghy capsized in the Manukau Harbour near the old Mangere Bridge.

A Mangere man, 45, and his 7-year-old son had been missing since their aluminium dinghy tipped over under the old Mangere Bridge, sending a group of five into the water. Rescuers pulled three children to safety.

Witnesses say children tipped into a powerful current when their family's dinghy capsized this afternoon were desperately calling for help as they clung on for dear life.