Visiting with his family from Canberra for the school holidays, Samuel and his younger twin brothers Liam and Eli immersed themselves among the marine life at Irukandji Shark and Ray Encounters at Anna Bay.

"It was amazing patting the sharks - I was a little nervous at first but they're like water puppies," he said.

It was a heart-warming sight for their father James who said his children were often scrolling on the iPad.

"I think it's great for them to get an experience that's different - it's not every day you get to swim with sharks," he said.

But his three boys aren't alone with the average Australian aged over 12 years old spending nine hours a day online, according to University of Newcastle professor of Education and Pro-Vice Chancellor of Human and Social Futures John Fischetti.

"One of the most important issues, we face as a society is what we're calling sedentary disease, which is actually doing too much sitting and staring at screens and being inside and not getting out and moving around," he said.

"It's probably the disease that will replace other diseases for this generation particularly our young people - Australia has 25 to 30 per cent obese children and a lot of that is from that sitting around."

He said while some of those online hours are legitimate there are two or three hours per day that are "wasted time" and there was a need to control consumption.

"It is in controlling the amount of time, just even by realising how much time is being spent - if three of those hours, we could take back. We're not trying to take it all," he said.

"Our kids have screens in front of them and there's really not a lot of risk in that if the content is appropriate, but what that's teaching us to do is be very passive," he said.

He said particularly over the holidays, parents could try different strategies to wean children off the screens.

"We need to try some strategies to wean our kids out and participate in the real world. Not just in that screen-based world."

And for Samuel, he said his school holiday activity was "much better" than being on an iPad or computer.

"As soon as I got into the water it gave me a bit of perspective - they may be big but they're gentle," he said.

Professor Fischetti said school holiday activities were excellent ways to learn new things and have adventures.

"I would choose them for teaching something not just killing time, so something like surfing or guitar lessons - something which is going to have a skill that lasts a little longer than the event itself," he said.

For Sydney father Matt Miller, it was enjoyable seeing his daughters Maddy and Mali interact with the sea creatures at Anna Bay.

"They love getting outside, being in the car while driving on the beach and having a barbecue - it's great," he said.

Maddy, 11 and nine-year-old Mali are both "iPad" kids but said there was nothing quite like getting to pat and feed sharks.

"I'm not scared of them," Mali said.

"You're not staring at screens when you're doing that," Professor Fischetti said.

He said getting children outside was a great way to get them to interact with nature and create new traditions.

"I think we can create new habits like whale watching, bird watching and riding bicycles," he said.

Port Stephens' Sibella Dawes did online school and said she preferred to get outside and do things rather than sit in front of a screen.

The 14-year-old was participating in the Mini Marine Biologist program at Irukandji where she got to dissect a squid, feed stingrays and snorkel with sharks.

"I just love sharks and being up close to them. I've always had a thing for them they're very fascinating," she said.

"I would rather be doing this than sitting on my phone, and it's exciting to get out and meet people."

Professor Fischetti said further ways to eliminate screen time were through children reading books, choosing a meal recipe and helping their parents in the kitchen, and implementing sensory activities.

"Kids can turn that sensory part of actually reading an old school kind of book - it's really important because it gives that sense of connection and then of course if it's with a younger child, read to them," he said.

"This creates bonding and nurturing which is part of literacy development in children."

"If you're stuck inside because it's way too hot or the weather is inclement, set up a reading corner inside your home or an adventure place. Anything that turns into a game or a fun moment increases happiness."

He said the toughest audience to crack was teenage boys who spend the majority of their spare time online gaming with people from around the world.

"Their social life is often involved in that, but it just creates an escape from being part of the whole family, so it's really trying to cut a deal to limit the amount of time. if they're on for two or three hours, could it be for one?," he said.

He said helping to knock back children from screens was almost like treating an addiction.

"The only way to stop an addiction is to cut yourself back. Most people can't go cold turkey it will just create too many arguments," he said.

"Technology is a necessary part of our lives. It's crucial that we use it well, it's not about turning them off. It's about limiting the use. We're just going to have to do better."