In some areas of Ōpito Bay, divers were only able to find an average of one legal-size scallop per 26 square meters of seabed.
The incident was filmed and put on social media.
"Having a wreck like this close to the shore, so complete, is pretty fantastic."
The man was filmed ramming another vehicle.
John Dixon is on life parole after beating a night watchman to death when he was just 16.
Children can be heard crying in the background.
The dolphins were swimming metres away from surfers.
He has been granted interim name suppression.
"That was the first time I've seen half a dozen full-sized hammerheads."