Itused sound propagation to navigate, communicate with or detect objects on or under the surface of the water, he said.
"It will speed things up a bit. We are still confident we will find him. It's not a question of if he is there, it's just a matter of looking.
"We have had three more divers join us from Wellington [today], making the total six."
He said the man's family were all back at the wharf on Otaramarae Rd yesterdaymorning as the divers left.
"We are hoping for a quick result for the family. As far as the dive squad goes, they are really optimistic and their search is going well."
He said the family had been back and forth between the wharf and where they were staying.
"They plan on sticking around until he is found. The locals have been bringing down baking and cups of teas for them."
He said the rahui was in place from the boat ramp on Otaramarae Rd out to the 400m markers in the bay.
"It will be in place until the body is found, then we will contact the iwi and they will come and it will be the family's decision on how soon it gets lifted."