Police have hit a wall in their underwater search for clues to the disappearance of an Invercargill boy and his stepfather.

Mike Zhao-Beckenridge and John Beckenridge have been missing for a fortnight.

Police think they've found a car under the water in Curio Bay in the Catlins, where a large amount of metal has been located in the rocks.

An underwater camera has been taken in again, but conditions are poor and it's not possible to be sure what's down there.

The plan now is to watch the conditions before deciding what steps to take.