A basking shark circles their fishing boat when Callum and his dad are taking in the creels. It is as long as their 16ft boat. They watch as the fin slices through the sea around them a few times. The whole sequence lasts no more than a minute, then the shark swims under the boat and is gone.
For most pupils, such adventures only happen in the movies. But for pupils like Callum at Kirkwall Grammar in Orkney, island life has many features that compensate for the lack of shopping malls.
Last year, a television crew from Caledonia TV in Glasgow began filming pupils at Kirkwall Grammar for a new series on Five called Over the Sea to School. Thirteen programmes were made over eight months, following the progress of children from different islands who are weekly boarders at Kirkwall.
"It is is a compelling story that children will identify with and illustrates our commitment to reflect children's lives throughout the UK,"
says Nick Wilson, controller of Five's children's programmes.
The series begins with the children preparing to board the ferries to leave for their new life in the hostel at Kirkwall's secondary school on the largest of the islands, known as Mainland.
Only 17 of Orkney's 70 islands are inhabited. The two secondary schools, serving a population of around 20,000 Orcadians, are Stromness Academy and Kirkwall Grammar, both on Mainland. Three junior secondaries on Westray, Sanday and Stronsay take pupils up to 16, and another on the island of Hoy takes children until the end of S2.
It is a big moment in these children's lives when they get on the ferry for the first time to go to "the big school", especially when they have come from primaries with only 10 or 20 pupils. They get home every weekend, but for mums and dads and brothers and sisters left behind, life will never be quite the same again.
Fourteen-year-old Drugh O'Neill is one of the pupils who feature alongside Callum in the series. Her name means "strong child" in Gaelic, and she lives up to it. During the week, Drugh stays at Papdale halls of residence, a couple of minutes' walk from Kirkwall Grammar. She travels to school by ferry from the island of Flotta at the beginning of the week and goes home on Fridays.
Drugh shows off the room she shares with her friend Holly, whose gold sandals, abandoned on the floor, add a bit of sparkle to the basic accommodation. The hostel is home to 70 pupils and looks and smells squeaky clean.
It is managed independently from the school, although Kirkwall Grammar's headteacher, Iain Ballantine, takes a close interest. The school has a pastoral care team of six teachers who monitor the educational and emotional needs of children. The pupils can transfer to Kirkwall at 12, 14 or 16, depending on the schools on their island.
"They have all the problems of homesickness; of being away from their mum and dad; of not having their own room; of meeting people from a variety of very different places and backgrounds; and of being confronted by the temptations of what to them is a much more diverse culture," says Mr Ballantine.
"The whole of Orkney is a safe place to grow up for young people, but in the north isles that's exaggerated even more.
"Although we are an island group," he adds, "we are not divorced from the problems of modern life. They are here, the same as anywhere else."
So what do the pupils miss most about home? "Hugs from my dad. I love my dad. I think I'm very like him and I miss him," says Drugh, sitting in the school grounds with Helen Le-Mar and Craig Horton, both 13-year-olds from Shapinsay.
For several years, Drugh was the only girl in her primary school, so she is delighted to have the company of other girls her own age in Kirkwall. Many other island pupils will have had similar experiences, stuck for someone their own age with whom to socialise.
Flotta is only 15 minutes away by ferry, but to travel to school every day would be an exhausting commute. "I'd have to get up at six every morning and wouldn't get home until six at night and then have to do my homework,"
There are only 100 people on Flotta, compared with Kirkwall's 7,000, so it offers tantalising opportunities for shopping, sport, music and cinema entertainment.
Like many in the Orkney islands, Drugh's parents came here from mainland UK, in search of a better way of life. Despite the lack of shops, the teenagers appreciate the quiet, peaceful environment and the sense of safety in small communities, where many homes and cars are left unlocked.
"My parents moved here from Dundee when I was six months old. They work at Flotta oil terminal: dad works on site and mum's a cleaner. And I've a peedie sister who is 9," says Drugh, prompting a brief introduction to Orcadian dialect, which Craig Horton sums up.
"Peedie means small, kye is cattle, coo's a cow and wap is a curlew," he says succinctly. He is a keen observer of waps and gannets and all the hundreds of other species found on the Shapinsay shoreline.
Having a film crew at school for the past year has fuelled great interest in media careers. Drugh has always wanted to act or sing and Craig is interested too.
His family left Lincolnshire for Shapinsay six years ago. His sister Fiona is in sixth year at Kirkwall Grammar. Their father, Clive Horton, is headteacher at Shapinsay Primary and their mum, Rosemary, teaches there.
"Here, I like the fact that I have access to all the shops and things in Kirkwall, like the cinema," says Craig. "You can go to the Pickie, that's the Pickaquoy Centre, there's a cinema there, tennis and squash, roller-skating and badminton. And we also go swimming at the school pool.
"Mum and dad wanted an island life, and, yes, it has lived up to their expectations," Craig adds. "It has nice scenery and people, and it's a lot cleaner. You don't get any traffic jams on Shapinsay. You only go slow if you get stuck behind a tractor."
Helen Le-Mar's mum is the only GP serving the 300 people on Shapinsay and her dad works as a property developer. Helen has a list of after-school activities in Kirkwall that wouldn't be possible back home.
"I do Irish dancing, play the piano and oboe, and play the flute in the orchestra.
"I like it in the hostel. You are with friends the whole time and there's lots of stuff to do. I don't really have time to miss mum because there's too much stuff to do and I'm home at the weekends.
"In Shapinsay I go for a cycle or go down the beach, and there's a dance every few months. We used to have a youth club, but the janitor left because there were too many risk-assessment forms to fill out. So we don't have a youth club any more.
"If you go to university you will have to stay away from home anyway, so I am getting used to it.
"I might be a musician or an architect. I'm too squeamish to be a doctor,"
The only downsides the three pupils can think of about hostel life are their three hours of homework and the washing-up rota. All of them would return to Orkney to live after further education, providing they could fulfil their career ambitions here.
For now, their main concern is struggling to remember if they said anything derogatory about their teachers when they visited the diary room while filming.
'Over the Sea to School' starts on Five on Sunday, September 3, 10.30am