My 12-year-old son, John, and I were in the middle of the North Sea, having set off from the Shetland Islands on a sailing adventure to explore the Norwegian fjords.

Home for the nine-day voyage was a cramped bunk aboard the Swan – a lovingly restored 107-year-old fishing smack, which normally carries Shetland’s youngsters on short school trips. Twice a year the Swan – made of oak with a larch and pitch-pine skin – takes a handful of paying passengers on longer journeys much further afield.

We arrived on board in Lerwick’s inner harbour, met the seven other crew members, stashed our kit, learnt the safety rules, donned our safety harnesses and got underway. Within an hour we had a mainsail and foresail up, and John was at the helm, tutored by our highly skilled skipper and ocean-going yachtswoman, Jane Brander.

Soon, off the nature reserve on the island of Noss, we hove to, briefly, to marvel at the massive clattering sea-bird colony perched on the 500ft-high cliffs.

Later, we took to our bunks early. The wind was light, but the motion of the relentless rolling sea took its toll. Lying flat and sleeping was the only way to fight our temporary seasickness. John woke first to stand his 3am watch. An hour later it was daylight and flat calm. We were a few miles from the Norwegian oil fields, the Swan’s engine allowing us to maintain a steady six knots.

“Dad! Dad! Come quick. Quickly. Dad! Dad!” Struggling dozily to put on warm clothing and a harness I eventually poked my head above the deck to smell the salty ocean.

Half a dozen pilot whales had been spotted off the port bow. John had watched in amazement as they swam first alongside – only yards away – then underneath the boat, before shouting for me to come up on deck.

But now… they were gone. The boy was full of it, beaming with joy at the experience. Me? I happily shared in the pleasure of his wonderment and cursed my own luck. Then, looking round, I had my own treasured memory – the stunning sight of a totally flat ocean, so calm the sea looked silk-like, shining as it reflected the early morning light, almost as if we were sailing through mercury. Even the seasoned sailors on-board found it mesmerising.

We pushed on for another 10 hours, taking our turns at the helm, keeping watch, or making coffee and tea in the galley for the crew. The boy and I stuck to sips of bottled water, nibbling on plain cream crackers to allow our stomachs to settle. “Big John” Simpson gave us a crash course in navigation.

After 200 miles we neared landfall – a small Norwegian island called Fedje. The charts indicated two different shaped lighthouses, one with gigantic white-and-red stripes. Sure enough, we could pick them out through binoculars from 20 miles away.

An exhilarating experience, to be exactly where you wanted to be. Ian Nicholson brought out a fishing rod and within 20 minutes he and “Little John” had landed 15 mackerel. More pictures for the family album. We had the fish – gutted and fileted – for lunch next day, cooked in oats and flour.

Three hours later we were tied up in Fedje’s tiny harbour. Like every little community we visited over the next week or so, Norwegians were keen to come on board and talk, on learning the Swan was from Shetland. Many Norwegians, having escaped the Nazi occupation, made the same trip from Shetland across the North Sea in small fishing boats, taking stores, spies and weapons to second-world-war resistance fighters. So frequent were these dangerous trips, they became known as the Shetland Bus.

They were the inspiration for John and I to make our own voyage. A group of volunteers rescued the Swan, which was retired from fishing in the 1950s. It ended up badly neglected in Hartlepool before being taken back to Shetland to be relaunched in 1994.

We spent the next week exploring hidden Norway, via narrow fjords, sailing close to small islands, wedged between forest-laden mountains. A 67ft boat can squeeze into places the bigger cruise ships can never get to. Consequently we saw a Norway only the locals know. We got to know our fellow crew members, and learn the Shetland ways.

We cooked and cleaned and shared the chores. We berthed in out-of-the-way spots, and went off exploring, often to seek a hot shower, before returning for our communal evening meal, with everyone taking turns at cooking. The Swan’s shower is wedged into a tiny closet, and very handy. But ashore, five kroner not only gets you blissful hot water but plenty of room to towel down afterwards.

We headed south for the wide-open stretches of the mighty Hardangerfjord. As we turned into this extraordinary water highway, surrounded by mountains, catabatic winds whipped across our bow. Led by our professional first mate, Magnie Sinclair, we put up more sail.

Our speed leapt from six to more than nine knots as we hurled up the fjord. Exhilarating doesn’t even begin to describe it. Late the following day, we gently manoeuvred up the narrow Maurangerfjord, a steep-sided arm of the Hardanger, to a small anchorage called Sunndal. Ashore, John and I trudged through rain for an hour, to the Bondhus Lake. Dozens of waterfalls cascaded down the mountain.

And on the way home a few days later, I was summoned once more from my bunk, early in the morning, by Little John. My son had spotted three killer whales 50ft away. I managed to glimpse a black dorsal fin as it plunged below the waves. Six months later we are still talking about it. And we are true seafarers now.

How to get there

Michael Bilton paid the Swan Trust £522 for his nine-day trip, and £405 for his son (01595 697406; www.swantrust.org.uk). Atlantic Airways has return flights from Stansted to Shetland, from May to October, from £172; www.flyshetland.com