Extra clubbies helped with the land search, climbing over the rugged rocks surrounding Mauao.
Surf Lifesaving New Zealand eastern region lifesaving and education manager Leigh Sefton said volunteers had been working in shifts to look after their own safety in the icy weather.
"They're getting pretty cold now ... We've got to pull them in. These guys would just keep on going."
Six men from a privately owned Tauranga commercial diving company joined the efforts on Saturday afternoon, as well as two local dive instructors.
Greenfield Diving Services owner Brendon Cappely said they were just taking the chance to help out.
"I've got a couple of young children around the same age [as Jack] and it's just a chance to help out. We've got the resources and equipment to potentially bring him home."
Around the Mauao base track, people were seen standing in groups looking down to the water below.
Another shift began at 4pm on Saturday with four IRBs sweeping the wider areas until 6pm, and swimmers in the water around the base of Mauao.
Western Bay of Plenty police acting area commander Inspector Karl Wright-St Clair said police would keep searching for Jack this week.
"We've been frustrated by the weather over the weekend. There's probably a window of opportunity early this week to bring the dive team back. There are plans for further land searches," he told the Bay of Plenty Times. "The best window for us looks like Tuesday or Wednesday."
Mr Wright-St Clair said Jack's family were yesterday starting to come to grips with the situation.